In a magic setting I am working on they have what are called Steam Rails. Big enchanted Engines that run on rails set into the ground. When you add water to the engine, it heats up the the water and turns the water into steam and the steam is then used to push the tires along tracks. Hence my version of trains. The water made for the steam rains on the road are made by Clerics who cast create water for the engines.

Magic is split up into 5 main different groups, wizardry Managerie (Mages), Soul searchers, clerical, and druidic.

Wizardry is the most common but very difficult to use cuz it take YEARS of study to do the simplest of spells. Wizardry is using knowledge to pull Magic out if the Magic world. Even after years of study some students may not even be able to grasp the magical knowledge past a certain level of magic. Enchanting is a school of Wizardy that can be learned.

Managerie magic is MUCH more rare it is people who are born with an ability to bend magic Natturally. It's more of a wild magic more powerful but less controlled like wizardry. Enchanting using Managerie magic could be very dangerous and so is not often done. It may work or it may make the Engine come to LIFE and start eating warm bodied people to power its self.

Soul searching is the ability to find the magic with in ones self, but again this can take years of study and training and learning and still not everyone is able to learn it. To enchant using soul searching magic would be to littural put part of your SOUL into an object which would be less than desirable to most people. There would not be enough of them selves to pass on after death and then you get ghosts powered by Engines.

Clerical is using the power of the gods, to use magic. People are wary to use clerics in stuff and for stuff as most clerics want to spread the word influence of their god and tend to take over where they work. The clerics who do work on the steam engines tend to be clerics to gods of mechanical things and invention so they enjoy working on the Steam Rails as they feel close to their god. The feel no need to take over as they are near their gods feild of influence. The only cleric that would be able to using enchantment magic would be Clerics of gods of machines. Except being a cleric they would most likely feel inclined to dedicate the Steam Rail to there god. Most companies feel inclined to keep there Engines to themselves as then the church and the clererie of that church might feel entitled to use the Steam Rails for missions of there God.

Druidic magic is the use if magic from nature. Most druids do not feel inclined to help upon a Steam rail which they find blasphemy to their way of life.

Enchanting by wizardry magic in my world is long and costly. It is pulling magic out of a parallel universe and putting it into objects. The more powerful the object the longer the enchantment. An enchantment of heat metal to the point of making 10s of gallons of water boil is a high level enchantment. The steam rail engines can take YEARS to make. It can take years as the only way to speed up the process of enchanting is to have MORE people working on the enchantment but then the more people working on the enchantment the more people must be payed.

There are other types of obtaining magic but that are rare and far between and often obscure. One would not not want to employ the type of magic for instance called Borrowers. someone who has traded his soul to a devil as they might afraid of a wrong step they Borrower would bring the wrath of their patron down on the Stean Rail.

My problem is that once steam trains are made someone will eventually stick them onto a carriage and then there are cars.

I do not want cars in my fantasy setting. The steam rails are supposed to be rare and have an magic sense to them. I need a REASON as to why people who not just make smaller steam run carriages.

My ideas was that the size of the magic steam producing engine cannot be made smaller than a certain size or otherwise they explode under the pressure of the steam. But if so why would they not make it out of a thicker or stronger or resistant steel for the engine...

Maybe the weight of the Engines is simply too much for the carriages but then why wouldn't they make stronger carriages to hold the engines...

To sum it up i need a reason why technology does NOT surpass that of trains and into cars. I WANT it to STAY at trains.