[eudamoniac]

I think you're underestimating how rich people most people are for the purposes of this discussion. The amount of people who would read but for funds is negligible. People spend their money on tons of useless absurd things every day. Money is not a main factor of the phenomenon of reading less.

[Desafinado]

I agree that it may not be the main factor but it's definitely a major one.

By the numbers wealthy people almost universally own and read more books. For a number of reasons.