Sure, I also do some things for free, but for the most part I need some form of revenue because 1) I have bills to pay, and 2) being paid is one hell of an incentive. Before advertisement (which, btw, if you mean that literally then we'd be talking about an Internet fetus) you were much more limited in the business models you could use to justify investing in producing content on the Internet. Youtube is a good example of that; I regularly watch channels that manage to produce content full-time due to the magic of ad revenue, even with the miserable share they get. Also, without ads, good luck running millions of servers and all that bandwidth without a paywall.