As someone who runs a content site for a living, I have to point out that using content as lead generation for a paid product or service, and monetising the content itself, are two different things.
Not all of your visitors will convert to a paid product, and, likewise, not all visitors will view ads. Entirely choosing one over the other is a missed opportunity — they can peacefully cohabit!
Making money from content is also damned hard, especially for anyone doing it on their own. Judicious use of ads is a good way to make a bit of money until other revenue opportunities take off.