(In theory if someone steals money through your debit card you can get it back... in theory. I'd like to avoid ever having to find out how well this works in practice).
They charge interest, but you don't pay any interest if you settle the full balance every month, which I always do.
Most merchants/payment processors include a premium for handling the edge cases that arise from credit-linked misbehaviour. In the same way you sometimes get a cash discount, removing the merchant/provider protections should show up in your wallet as a good (and surprisingly high) surprise.
As I understand it (please correct me), the party who gains for the furtherance of this agenda is the financial service sector who has another opportunity to insert marginal fees and more importantly, a direct access to your transactions without necessarily having the same fiduciary duty or alignement of goals than a bank teller/account manager would have.