Monopolies weren't allowed to do things that non-monopolies are allowed to do because they would have an outsized ability to harm consumers as a monopoly. But Amazon has repeatedly shown that it isn't harming consumers. In fact, it's pushed other retailers to better the customer experience or go out of business. Should a company be split up just because it's doing its customers good and got too big because... they're doing their customers good and people like that and want to give them their money?