Dating, porn, and other popular markets aren't hard at all. The smallest degree of innovation or critical thinking will give you that meager portion of the market that makes you money. When a market is said to be "saturated," it really is never completely saturated -- just full of people copying eachother. Innovate or bust.
I think travel is hard because it's a multivariable market instead of a horny guy looking for some fapping material. Same with some financial markets.