I recently tried logging into Diablo III after about a year - I still knew my username and password, but the account was locked. The email address to reset the password no longer existed. When I contacted their (very hard to find) support line, the expected wait time was forty five minutes - they wanted me to wait forty five minutes so that I could beg someone to give me access to a product I've already paid for.
The point is - email addresses can be hacked just as easily as account names and passwords. There are plenty of moments when people delete an old email address - maybe they were being harassed. Maybe they were starting a new relationship, and they didn't want old flings trying to get in contact with them - sending a message about casual six while the new girlfriend is surreptitiously looking over your shoulder. (Can I say awkward moment?) It could be a matter of simply wanting a newer (and cooler sounding) email address - I've done two out of four on that list.
If losing an email address, or deleting one without thinking about "Oh, this is used for XYZ games," and that then results in losing access to products that I've paid for - I've been burned twice now. The first was Final Fantaxy XIV, and then with Diablo III. I'm at the point where if something requires email verification to simply use the game - considering that email addresses can be lost, hacked, stolen, or deleted - I probably won't bother purchasing...