>>8091125Like a lot of the ST, its a hard turn from the PT's more extravagant fantasy designs and based on a misinterpreted bit of design philosophy from the OT. The OT did have some characters wear contemporary 70s fashion, Luke's feathered hair being a notable example, as is Han's casual work clothes. So the ST costume designers just went full force on that and everyone is just wearing t-shits and jackets and modern haircuts, with maybe some piping or ridges here or there
The other thing is the trend towards "cosplayable" looks, companies like making costume design that are easy for fans to put together and wear. The idea being its good free publicity to have people show up to your movie premier in costumes.