I assume your circle is mostly tech people? Outside that bubble, it's pretty obvious. People just want easy, don't understand security in many cases, it's the simplest path.
Even absent the above. Imagine a signup flow. I can either click <Sign Up With Google> or I can go through a manual flow with input fields. The former is much faster than the latter. It surprises you people choose the path of least resistance?
It does not surprise me that people choose the path of least resistance. I find it sad that they happily connect everything to Google/Apple.
What surprises me is that it is a "conversion killer". So if you ask people to create an account, it's sooooo very hard for them that they will just leave. And spend the next 30 minutes scrolling TikTok, I guess?