Because for some bloody ridiculous reason we keep being told Twitter matters, because it's managed to leech into the internet nervous system and keep itself alive by symbiotic clickbait articles on Twitter mobs sending everyone round in circles, so that government bodies and various authorities think they have to wave their credentials on there. And because they've invested in this kind of multi coloured virtue display, with no bloody thought about how a fist appears, even if it is in pretty colours, they think that it counter-balances not doing all the other stuff they're supposed to do.
Twitter is cheap, basically. Cheap, shit, and needing to be binned off so that it can be dismissed along with all the nonces and creeps who currently reside there.