Well, while that's the main reason, there are indeed some side benefits as well. I guess the first one that came to my mind is, I got rid of a lot of spams. Mostly because my Gmail address was in lots of breached websites. I also deleted any unnecessary accounts at variety of websites, because of these I haven't been in a breach scandal since 2019 (That's the year I finalized my transition to Tutanota). I use it on my government accounts, banking accounts and any other formal accounts, or the ones I trust. For the rest, I use email alias services and if I get a spam or even an annoying mail through that, I can just stop it there and I forget about them.

Also it's not just warm fuzzies. Privacy is a basic human right and it should stay that way on the internet as well. So it's nice to know to be freed of personalized ads hell, at least from the voluntarily part. Can't really do anything for the involuntarily part besides GDPR. Big corporations getting our personal data is not different from someone watching my house with a binoculars, same level of creepiness. I don't think any sane mind would be comfortable knowing this.