Earlier quoted context omitted.
it has not evolved much. and i believe that's a good thing. this is the reason why emails from 20 years ago look the same even if you open them today. given the short life of everything on the internet, email is a wonderful thing.
Yes, I have no idea why UI practices need to constantly "evolve". As far as I am concerned a lot of UI is getting worse over time so the less evolution the better.
Also humans seem to need fashion as a mechanism to show belonging and distinction. (Differentiate form parents generation, show affiliation to some sub culture, ...)
And then there is the hope to make the production more efficient. (Which may not work out)