[electric_sheep]

Many of those patterns that you list aren't actually trends resulting from received wisdom -- they're dark patterns, known to be actively hostile to the user. Common wisdom regarding UX would vigorously contraindicate their use, but they continue to be used because people either don't know or, more likely, don't care.

[avian]

I've seen these dark patterns justified by "UX experts" like so:

1) Make a A/B test with an annoying pop-up sign-up box and an ordinary unobtrusive one.

2) Data shows that more people sign up using the pop-up.

3) Obviously people want to sign up, but can't find the unobtrusive box.

4) Hence, the pop-up design helps people achieve their goal (of signing up) better and is therefore more user friendly.