From the consumer side, I don't use it all that often for purchases just because I'm aware of the interchange fee tax on cash purchases so I try to maximize the value of my credit cards: 3x Avion points for grocery spend on RBC ION+, 2 Aeroplan pts/$ for dining on Amex.

As far as a requirement to be online, given the nature of debit that doesn't surprise me; the whole point relative to credit is that no one has to trust you to pay a bill later. If offline transactions were possible then it would just be a credit card by another name.

The refund thing surprises me, but I expect that has to do with preventing some fraud scenario, maybe like an inside job where an employee issues remote refunds to a confederate? Overall it seems like the design of the system is fairly conservative and that's reflected in the much lower fees; the whole point is to not have to have whole armies of people answering the phones to help grandma get back $50.