You can often make a reservation without providing billing information, so there's no mechanism to enforce a payment for no-show. If you prepay for the rental it's different, but there may also be a significant discount.
I do feel the remaining rental car businesses could live past their reluctance to enforce a partial reservation payment. A single day’s payment (for, say, one week’s rental) I feel is reasonable or $50.00.
Especially if it means better service, better cars, and a more consistent experience.
However, I only rent for vacations and I may be blind to the what the average renter demands/expects.
I may be in the naive minority, however.