The users who saved their $15 can't afford (or won't pay for) as much stuff.
I'm not saying you're wrong, but I don't think it's as straightforward as you indicated.
Also, the ads are not on the media itself, nor do they interrupt it. They are not intrusive, and do not bother me.
I know lots of people that have >$500 dollar phones, who refuse to spend any money on apps. They only install free apps - it doesn't matter if a one buck app will save them time or money, they want free apps and only free apps.
I am fine with ads for free services but death to you if want to be paid twice.
For the company to get the same amount of money, the trade-off curve looks something like this:
Pay $x, see 0 ads.
Pay $0.75x, see 1 ad.
Pay $0.5x, see 4 ads.
Pay $0.25x, see 20 ads.
Pay $0, see 50 ads.
Some customers prefer to pay with their eyes instead of their wallets. You don't like to do that. I don't like to do that. But it's fine that companies give us the choice.
Also, you pay for broadcast TV?
Zynga? Giving "choice" back to their customers? I'd say that's a stretch.