You know how much junk mail I get, most of it could come back to bite me in the ass. Shit like credit card offers and insurance and other bs like that. Yet, reguardless of the amount, I still get more. So it doesn't matter how much shit they send out, they'll send out more, just for that chance that I'll buy some of thier over advertised crap.
Email is no different, it's even cheaper than the US mail that comes 6 days a week... but email is sent out 24 hrs, 365 days/year. Even a penny vs the 39cent/mailing is well worth it for advertisers.
At some point, someone (ie, political knowidals) need to come in and put some sort of foot down. Just say, fuck you, No....damnit i could go on, but then it'll become a rant....