Being a little pedantic here, but the picking up the tab for the failed suppliers really means securing the money for the consumers who were owed money by their suppliers, plus compensating the other companies for taking on new customers that they would be forced to sell energy too at a loss.
I think we would all agree that we would all be wanting, our money secured should we be with an energy company and they owe us money, and that we would all want to be able to move onto a "normal" tariff should our energy company fail.
Imagine if you were unlucky to be with say Bulb and instead of being moved to a capped deal you were moved to a deal that had your typical bill placed at £4250 a year (which is roughly what it would have been!)