I think it's also because every site wants their buttons etc. to look slightly different to every other site's, because branding. Being able to stand out from t

I think it's also because every site wants their buttons etc. to look slightly different to every other site's, because branding. Being able to stand out from the crowd is a feature. Personally, I wish that for accessibility and other reasons, all 10000 frameworks would produce buttons with some kind of metadata that lets a user configure their own settings. But we're quite far off that.