Brief and quite simply,
The same reasons there's difference in tech-levels here on our earth now:
Technological Development, Time & Distance, Society
A bit longer and somewhat more elaborate,
The different planets are simply lacking the equipment to manufacture certain things, after all: building a factory requires another factory that produces the more basic things. Transporting everything between planets with our current technology-level is simply not feasible
Time & Distance:
Another thing is the actual distance and thus time it takes to colonise a planet. For example the mentioned planet Jupiter is, at it's closest, still some 600 million kilometers away from earth.
At the speed of light jupiter'd then be approximately 32min traveltime from earth (give or take some1).
According to wikipedia, the record for the highest speed relative to earth ever attained by a human being has been achieved by the Apollo 10 crew in 1969 (20 years into the colonising idea/effort); the achieved speed was 0.0037 percent of the speed of light.
So even by ramping up the fastest speed we've attained travel times between systems and thus the time for someone or something physical to actually reach another planet are still tremendously long.
If society does progress along the same ways it did on our earth, then Planets might as well be regarded different nations.
Patent law and patent infringement will be a big thing and the planet might simply not have the money or lawyers... After all they will likely still need to rely on earth for things that cannot be made/grown on other planets due to radiation and other concerns.
So here's some reasons for you based on distance and enviousness
1588'000'000'000m / 299'792'458m = 19612s = 32min
2funny enough, this is also the year that JFK became president
On the Issue of Distances:
As mentioned we could probably send a single signal to Jupiter in some ~32min (with lots of leeway). Thus a signal roundtrip and thus the span between two messages of a fluent conversation would be some 70min (give
Now we know, we could send the plans for a new coffee-maker and other technological novelties in a negligible span of time.
So what's the issue?
They can't build the coffee-maker... All the computers and tools we sent with them are decades behind everything we have on earth. Even if every new ship we send with supplies, crew, and materials will be some 10%1 faster than the previous ones they'll still be on their way for years.
But they could build machines to build newer machines, that's after all how it works on earth, doesn't it? - You're right there! But that isn't going to be that fast a process, they'll still need raw materials, many of which they will need us to supply them with (e.g. plastics). And they will likely not be able to build any factories that create large amounts of parts, so their production facilities will be occupied for producing basic parts and machinery to make repairs and replacements of their habitats/spacestations/wherever-they-live.
1The number of 10% is highly fictional and will steadily decrease to a point where improvements over previous speeds will have to be measured in the area of 10-3% and less
On Technological Development:
All the above does not mean the technical development of earth and its colonies will be the exact same as in our universe. The act of colonization will likely lead to a science-/technology-boom in areas such as Environment Control & Manipulation, Isolation, Thermal & Solar Energy Production/Recovery, Robust Electronics, Rocket Science, and many more.
It will also be likely that our mars habitats actually have technology that has roots in our smartphone technology (our rather the other way around if we're looking at it more closely). But that colony we've established on Io 5 years ago pretty much will still be on the tech-level of the late 60s.