Its the same question you have to pose to ALL fantasy lores (except maybe steampunk). If Magic exists in such quantities, why hasn't it been put to extremely efficient and practical use?
Why aren't the wealthy riding around in feather gliders? Why aren't they driving in steam powered cars powered by flame atronochs? But it ain't Bethesda that's guilty of overlooking these things... its practically every fantasy system ever proposed.
You have said it, in pretty much every setting, it's just like in the Elder Scrolls, magic is never used to bring about all the conveniences for everyday life it could. In some settings, they will give some kind of explanation, such as having those who can use magic be few in number and mostly removed from society (or they just don't want to bother using their magic to make people's lives easier.) in others, they just assume people won't think too much about it, given how common magic is in Tanmriel, I think it's more of the latter. I believe the reason is a matter of feel, for most authors "fantasy" means a watered down version of Medieval Europe except with magic and dragons, so they do that, maybe you'll get a magic civilization that uses magic for every day life, but for most, magic is pretty much separated from mundane things, because if people started using magic powered aircraft or vehicles that use fire spells as a substitute for internal combustion engines, it would go against that cliche, and for fantasy, anything creative seems to be something that will be avoided at all costs.
I think most mages in Tamriel have learned from the Dwemer's example of undoing themselves from existence enough to stay the hell away from science.
The Dwemer tried to use profane tools to steal the power of a god from his heart, that's a very different matter from using steam power or finding more uses for gunpowder.
Probably for the very same reason there are still fairly rotten area in almost every first world large cities : those who need the fixes can't afford them, and those who could pay don't care. They might have the technical ability to do it, but won't do such extensive effort out of the goodness of their hearths.
Look at real world Detroit : it's in the wealthiest, most technologically advanced country on the planet, yet large parts of it still looks little better than a 1945 german city. The technology and the ressources to fix it up exists, but nobody's willing to fork the bill.
But if you go to the places where the people who CAN afford that technology are, in any developed part of the world, you're likely to see all the things that we associate with modern technology, it isn't so in the Elder Scrolls world, though, even the Imperial Palace seems pretty mundane, just bigger than every other building in the Imperial City, you would think that the Empire could afford to hire some mages to do some nice things with it, it would certainly command more respect to the Empire if the seat of its government was made a little more impressive.