The advancements made in the past 100 years or so are unprecedented in human history.
Even still, all over the world you can find people who live exactly like their ancestors did, going back 40.000 years.
Status quo is the natural mode, advancement or change is rare.
Tamriel is 6500 years old and also a mythical universe.
The factors that stimulate progress and change are largely absent.
Some of those people who didn't advance much past their ancestors 40,000 years ago simply are that way because of geography.
Before I go on about it, maybe I should suggest Guns, Germs, and Steel, if you haven't read it.
Some people had a limited network. More importantly, some people based their societies on a handful of crops - crops that had secondary, subtle effects on their way of life. Some tribes in Africa, for example, sustain themselves almost solely off the bark/skin of a certain type of tree. It requires a lot of work stripping it and preparing it - and they can't even store it for long or it will rot. So all they end up doing is working hard and then eating. They can't store their food, they have little down time for recreation, let alone creation of new projects. They didn't have the means to simply reinvent themselves and think of new ways to evolve.
Needless to say, in TES, some civilizations are not this way. They have plenty of time to invent. I guess you could say that a lot of mages make use of this the most. It's probably the most evolved "technology" (if we can call it that) in this world. But I'm surprised we don't at least see a scientist like Da Vinci, making advanced war machines or something.

