Force field technology has come a long way. The latest energy-efficient engines can guarantee stable energy output in any situation, making force fields extremely reliable and very cost effective compared to acrylic and glass. Power failure is a thing of the past. Force fields eliminate the need for decompression chambers because the fields can allow both organic and inorganic objects to pass through unharmed while preventing air from escaping. Given such a future, why would any spaceship still have acrylic/glass window?
The short answer is that they wouldn't, but not for the reasons stated in the question. Longer answer is as follows;
First of all, even assuming that power is ultra-reliable, it's good engineering practice to build things where the safety position is in the 'power off' mode. Modern nuclear power plants (for example) don't need power to insert the control rods that slow down the reaction; they need power to retract them. When the power cuts out, the control rods fall back into place, effectively shutting down the reaction while there is no power, and therefore no monitoring or control.
A window is the perfect 'power off' safety solution in your case; if the ship is the first one in 100 years to lose internal power, then your crew is still safe from suffocation, at least in the short term. With force fields, they would instantly be sucked out into the vacuum of space to suffocate. That's not a good 'power off' scenario and no-one in their right mind would build a ship like that no matter how reliable the power supply appears to be.
Second, it should be pointed out that with the exception of airlocks, they probably wouldn't use glass windows anyway; they'd most likely have display screens on the inside and closed circuit cameras on the outside. This has 2 advantages. The first is that there is no structural weakness in the ship caused by putting a window into a solid bulkhead. The second is that you can look through every 'window' from a single display screen, making it more versatile a system.
As for airlocks, you'd still have a blast door that you'd shut for the majority of the time because of the 'power off' safety consideration, even if it was only for the psychological comfort of your passengers and crew.
Finally, there is no such thing (even in the future) as a 'reliable' power source. EVERY power source either contains or generates power and releases it in a controlled fashion. It's that control which often generates the issues and when the control is less than optimal, the power can be released in an uncontrolled fashion. Think Fukashima or Chernobyl; in both cases, massive energy releases occurred because of unforeseen (read as unplanned for) circumstances.
What if your ship takes longer to get where it's going? Runs out of fuel? Runs into an asteroid? Gets attacked? Something can always go wrong with a power source. People who think of something as reliable (IMHO) just don't have good imaginations.
Bottom line is that you don't want the power to go off on one of these things for the first time in centuries to be the one time that you get asked why you put a permanent hole in the side of your ship in the first place.
there is reliable and there is reliable, solids work even without power, even in a magnetic or radiation storm. Your power source may not fail but connections can be cut or damaged. And of course you have power usage, a force field will need a lot a power a plastic plate needs none. Solids also offer protection from radiation and micrometeoroids which your stated force fields will not. Finally you have purposeful loss of power, turning power off for maintenance is pretty normal for safety and not having to run extension cords to all your windows to do routine maintenance is a big bonus.
Because maybe the field needs help, or maybe you want to keep people from getting zapped by the field.
the fields can allow both organic and inorganic objects to pass through unharmed while preventing air from escaping.
If the force field is only good for gas, then probably you do not want your stuff falling outside the ship when you turn a sharp corner. Or stuff outside falling into the ship - though that outside stuff can be moving fast and hopefully you are not counting on an acrylic windshield for meteoroids. The areas protected by your futuristic fields are separate controlled zones and you want to control access to these zones by things and people.
If you assert that your force field can exclude people and things as effectively as gas, then maybe it is unpleasant for people to be excluded by a force field. It hurts. You do not want to get out of the shower and accidentally walk into one wearing just a towel. An acrylic shield is a reminder to humans in the vicinity: Force Field here. Keep arms and legs out of the force field.
You could use a chainlink fence for that instead, or "CAUTION" yellow tape. But the acrylic looks cleaner.
You can't never trust in things like your energy production or a force field.
What would happen to the ship is it run out of energy? For example: an electromagnectic pulse could shut down your reactors or damage the internal system of your shields and all the people would die almost instantly. That ship is extremelly vulnerable to lack of fuel, hack, reactor overload, EMP, failure, etc.
A good engineer always designs things with double check/security systems, like a forcefield and a windows (also, you would use a camera and an screen instead...). An engineer would dessign ships able to hold life even on a power off situation like the described above.
If the ship accidentally has a failure it mustn't produce a bigger problem, it must try to fix or prevent it, i.e: if the ship shut down, the airlock must automatically close itself not open.
Actually there won't be glass or acrylic screens at all. In planes, the windows are actually a weak point.
You can use screens and cameras to emulate windows without the structural weakness of a window
Over the next twenty or so years, windows will disappear from aircraft
Shields will make a good backup and emergency repair but you can't really use shields as structural strength.
If the force field behaves how you want it to, there is indeed no need for glass or acrylic screens. I believe this was mentioned in one of the star trek movies/episodes were they didn't actually have any glass in the windows.
The point of screens in most sci-fi, even when force fields are available, is that your force field can only only withstand so much, before it is destroyed/penetrated and so one. When this happens, your screens will protect the personnel on board, instead of creating an instant vacuum and sucking everyone out.
Secondly, it would be far more energy efficient to only use the force field when its required, rather than projecting it 24/7 all year. Space journeys can take a long time and a space ship can only hold so much fuel and spare parts before you need a bigger spaceship, which requires more fuel and so on.