"Medieval" isekai: why a horse-driven carriage instead an armored all-terrain vehicle?

Except the argument that they keep coming back to is "because magic" as a reason to ignore every reason, cost feasibility WAS brought up before by the way, not just here but in a LCD thread the OP asked it in before posting this.

Aircraft carriers are on the line of cargo ships, this thread was on stuff closer to luxury cars. To be more specific the question was why in a worlds were medieval european transport vehicles are the best available ANYWHERE does the MC not just make a (armored) magic car instead of just improving the vehicles available.

What I have been saying is that there needs to be both a reason why the MC can make such a vehicle, and why the rest of the world does not have any, which only makes sense when the MC has a cheat like in Arifureta (why the rest of the world can not make one is explained well before he acquires the skill needed to make his hummer) or most of the knowledge is there but a key piece is missing (which requires magic and materials alone to not be enough). Keep in mind that with a magical power source that can be used to rotate a wheel, you could make a vehicle with medieval level knowledge of windmills as a basis for a transmission and most series are set in a society developed well past (ie : several centuries) the point windmills, crank shafts and even pistons were developed, and simple steam engines existed in Ancient times let alone the medieval, and magic materials would likely solve allot of the issues that they would have in being used as a power source.

Costs involved is one of the reasons brought up as a potential reason why not.
Other potential reasons include :

The settings level of magic is to low for such a vehicle to work.  the time involved to develop and fine tune such a vehicle could easily exceed what is available to the MC (in the thread I mentioned before the MC has less than a month to make a vehicle, and has never made anything with parts moving by magic, but went overboard on the rest to the point the local lord saw it, asked how much it would cost to make one, and placed an order)knowledge, very few actually have all the necessary knowledge of how the engine, transmission, cooling and everything else in a car works. needing to blend in and not stick out to much (these could paint a big target on the MC's back, and in most series they are not actually invincible, immune to assassination or strong enough to take on the whole world)potential fuel efficiency (which is related to cost), does the vehicle need some form of fuel, or can it recharge and if so, how long can it run vs how long does it take to charge? There are some series where you see vehicles and mecha that can operate for short periods of time, and require long recharge delays. The nature of many magic systems does not lend itself to these types of creations (seriously in many series the nature of the MC's magic of skills does not mesh with making a magic vehicle)

 

All you need for transport is a can of magic beans, travel with the power of farts. 

Personally, if you're going for the ultimate magic transportation. Just get an Air Ship.... 

coming back to this thread because of a like notification, i'm amused at people seeming to miss the point and looking at the problem realistically. This involves isekai and when has that ever been realistic?
OP also mentions having magic and magical materials.

The arguments, when looking at the idea realistically, are sound but that's not what the question is asking. 

that would be super incovenient cuz in medieval ages, the poops were all over the streets so if there's water jet coming out of the vehicle's rear, the people behind would get all the sh**-water jet splashing like crazy 

I think that what the MC did in RTW is quite realistic, he knows how to make it but couldn't, thats why he used the people that who can use magic to make his ideas. Besides, he made a nuke in the and so who cares about tanks. ... well, he did make tanks and planes and trains and at the very end the SHIELD flying carrier. So yeah he makes a lot of stuff. 

I'm a bit confused why so many comments think that building a car/tank is somehow better than a horse carriage? It's a common misconception to think that what we have now is the ideal rather than a compromise due to lack of technology.

There are plenty of advantages of a horse drawn carriage over a vehicle. One advantage as stated is being low key.

But there are other possibilities such as the fact that horses can be replaced with golem horses. Or magical beasts. Then you can just tell them "get me to location A" and you don't have to drive yourself. Horses can also be used in places that cars can not. 

In "Yasei no last boss ga arawareta" MC, made a RV Golem