It's not old, no. but then not sure many guys in their early 20s normally look for guys nearly double their age in their normal sex lives. saying it's "common" is probably only true in very hyper-liberal spaces, and it's like cis people. Few cis guys or girls in their early 20s date men/women nearly 40. Paid sex is different to normal sex, but then i'm genuinely interested if they mind or not.