Why is adaptive power steering in cars horrible? Why is an integrated computer-controlled console horrible? Why is a computer-controlled refrigerator or dishwasher always horrible? Or a CPU running your stereo with a touch screen.
There's no inherent reason that computers should make these things worse. But they always do. Computers always make things much much worse.
The reason is that the designers just can't resist the temptation to fuck things up. They could just make it so that when you turn it on, it instantly shows you buttons for the things they want to do. But no, they think "hey, we could show a video here and play some music when you turn it on". NO! Don't do it!. Or, when you turn your steering wheel they could just turn the car wheels by a proportional amount, but they think "well we've got all this computer power, how about if we detect if you've been driving aggressively recently and dynamically adjust the maps". NO! Don't do it!
Furthermore, in practice adding computers is almost always done as a cost-cutting mechanism. They see it as an opportunity to make the mechanical function of the device much worse and then compensate for it through software optimization. (see for example, removal of mechanical differentials and replacement with computer "e-diffs"). It doesn't actually work.
I was thinking about CG in movies and how uniformly horrible it is, and I think it's roughly the same problem. It's a sad fact that models still look massively better than CG (for rigid objects anyway, buildings and space ships and such). I've been watching "Game of Thrones" and it looks absolutely beautiful most of the time - the costumes are great, the sets are great - and then there's some fucking CG shot and I want to vomit. The space shots of the Enterprise in TNG from like the late 80's still look amazing (when they aren't firing lazers or any of the bad CG overlays) - just the model shots.
Part of the advantage of models is that it forces you to be conservative. With CG you can choose to make your spiderman have weird stretchy motion - but you shouldn't. You can choose to make a chrome spaceship - but you shouldn't. You can choose to make the camera fly inside an exploding skull - but you shouldn't.
I also think there may have been an advantage with models in that they were difficult to make, and that meant you had to hire actual artists and craftsmen who had honed their skills and had some taste, as opposed to CG where the barrier to entry is so low and it's so easy to change, it makes it much easier for a director to fuck things up, or for teenagers with no artistry to make the shots.