Those are so infuriating. Especially when it's for some random website that you'll likely never have a reason to visit ever again. Does anyone actually subscribe? I highly doubt it, though who knows what old people do (I used to do end-user tech support and I've seen some shit). I've come across a couple of stores offer a small discount if you subscribe, which is at least a legit reason to do so, but this discount is so small that I even then I don't bother.
Surprisingly, yes. I have no idea why people put their email addresses in those things, but they do. I put a tiny email capture on one of my websites once as an experiment. I didn't even offer anything, It just said "Keep in touch", and thousands of people signed into an double opt-in mailing list in the 3 weeks I had it up. Fucking weirdos.
I always wondered does anybody (with sane enough understanding of tech) accept notifications? It's the one thing I hate the most, it triggers anxiety and takes my attention away from what I have to do.