Since late 2019, why are we seeing a massive increase in pop-up notifications, and why do UI designers think this is a good idea?

This might be slightly broad, but I think most of the questions on this site are somewhat subjective and broad anyway.

Since about late 2019, the number of pop-up notifications and potentially similar types of notifications has suddenly increased dramatically. Every other time I open a website or a program on my computer, even if it's something I use every day, I keep having to dismiss notifications that I simply don't care about. Quite often these notifications are designed to let the user know about certain updates and UI tweaks . . . but they're completely irrelevant 99% of the time and are quite stressful and distracting from the core features of the website or program.

Stack Exchange responded very well to a related question and has generally kept their sites very clean from this type of thing. Personally I feel that is one of the reasons Stack Exchange is as popular as it is: While it does provide notifications, they are generally relevant, and they are generally not distracting pop-ups that have to be dismissed.

In that context, notifications are great, but pop-up notifications and irrelevant distractions are deterrents against continued use of a site. So why, just about everywhere else except SE, have pop-up notifications suddenly multiplied since late 2019, and why do UI designers not see this as a bad thing?