[hmlongco]

Probably the fact that while you listed your preferences you and most everyone else wouldn't bother to pay. Primarily since it would mean making a credit card transaction to an unknown site.

Your options are clearly biased towards the fact that you don't want really to pay anything, either in terms of money or ads/attention.

[SilasX]

No, I've paid for courses before, far more than I care to admit. And I've listed an ad-based option that makes money (2), I'm just allowing for the possibility of people who want to get paid in self-promotion (3), although that's perhaps redundant, being a species of advertising.