It's just a statement of orthodox economics; more people work on these things because they pay better. There's more money in advertising than difficult vague projects for the betterment of humanity.
With a PhD + 7 years of experience, you make the princely sum of $61,308. Due to how research funding is structured, it is very difficult to negotiate a salary that's much above this. These jobs tend to cluster in expensive areas (Boston, NYC, California) too.