Architectural Lighting Designer here, they probably aren't a fad, but manufacturers are working on developing fixtures where individual components are more easily replaceable so that the whole fixture doesn't have to be replaced.

There is also a conversation going on regarding whether the waste from replacing fixtures and emissions from manufacturing outweighs the ecological benefits of using less power with LEDs. The current answer is probably yeah it does, but manufacturers are reluctant to provide concrete data on that sort of thing.