While you may never read them, a surprising number of people do. I had an internship where my primary responsibility was composing HTML emails that went out to users on a weekly basis. If I remember correctly, the majority of our users opened the emails, and roughly 5-10% clicked on a link to content on the site. I imagine these number vary quite a bit, but for a site with a paid membership we saw a lot of traffic from HTML newsletters.
Indeed, many people enjoy reading content in their email client and prefer it over other delivery mechanisms. (Some people live in their email client.)
No, I don't receive any mass-delivered email that opted-in for, because if I wanted to read something generic I would go to the relevant website or blog. I do, of course, receive some 'group email' which is equally relevant to all the recipients, but the sender obviously had all of us, recipients, in mind when writing the email. And I'm not even opposed to mass-emails, it's just obvious that for the most part these emails are not relevant to the recipients, and adding any styling to these advertisements isn't making them any more relevant or useful.
I frequently receive marketing emails from sites I never opted into. Either the site didn't provide a choice to opt-in or opt-out on the same form where I provided my e-mail address or they ignored my preference.