But, couldn't they make the tradeoff more explicit and transparent for the customer? "This ticket allows you to be bumped, for which you will be paid $X. You can pay $Y more to make it a permanent you-own-this-slot-we're-not-f'ing-around reservation."

None of this, "oh, you didn't read and memorize the minutiae of overbooking policies and have to figure everything out minutes before the flight you thought you were going to be on!"