I think a lot of it is because it is "free" for those that already have a prime subscription but also there's decent content via freevee for those that don't want to pay.

Bosch and the follow up Bosch Legacy are pretty solid series that Amazon is suprisingly offering via freevee. I just binge watched the latest season of Bosch legacy and just muted the 1 - 2 minutes worth of commercials when they'd come up.

I haven't used freevee much but from the little I've looked at it seems like they've got some decent stuff on there.