The Bachelor is a great marketing case study. The "trailers" are tantalizing, but ultimately, lack a payoff. The episodes are shameless in delivering exactly what customers want: drama, suspense, sex, and emotions, all wrapped in the package of romance.
Any show can go 3 seasons without broad appeal (Friday night's lineup, notwithstanding). The Bachelor keeps churning out a product in demand, season after season. The producers give their targeted audience what they want - and fix mistakes quickly. Advertisers are willing to pay up in order to reach that targeted audience.
And the audience continues to consume. Nom, nom, nom. The product doesn't need to be "good." It doesn't need to be valuable. It just needs to be in demand. And this product will always be in demand.
Disclaimer: I don't watch the show, but my lady does. I receive a thorough weekly update (by request). She receives a "Bachelor through the marketing lens" response in return (not by request).