these are "prison chic". When young men are locked up in the USA they take away their belts (in case they try to hang themselves); so their trousers hang down a bit. So kids on the street try to dress the same way to make themselves look well hard. And manufacturers have jumped on the bandwagon, making trousers that exaggerate these characteristics.
Plenty of fashionable clothes through the centuries have been uncomfortable, so that's nothing new: high heels, wasp waists, 3 foot high wigs... People put up with it because they want to look cool.