I've come to believe its a mix of virtue signalling (public, empty gestures intended to convey socially approved attitude without any associated risk or sacrifice.) and pat-yourself-on-the-back slacktavism (there, I tweeted about what people perceive to be a problem, therefor I've done my part).

In essence, they get to tell themselves (mostly convincingly so) that they have contributed to reduce inequality and discrimination, and are helping right a historical wrong.

In the end, I dont think it changes things one wit - but it makes people feel better, so I guess its a net good over time - albeit an unconscionably silly one.