Because Twitter doesn't want to know all the rubbish Facebook wants to know. Facebook wants your whole life online and available through Facebook whereas Twitter doesn't care what you do with your account. You can share your life or you can talk pop girls all day and not actually reveal who you are. It's your decision
Nobody I know uses it anymore. It's sad tho, back in the days, until around 2013, Twitter was lit. I loved being on there. I hope it makes a comeback soon, because I don't feel like posting random thoughts etc on Facebook.
Maybe because twitter appeals to everyone? And celebs are actually there, not via management like on Facebook. Probably the same reason snapchat is slaying.
Most of the people from my school stopped using it around 2013/2014 though.
I don't know what happened to Facebook but where I live, the over 30s/unemployed mostly use it.
I think it will decline though. As the censorship increases "alternate" Twitters will get popular. People want to Tweet gay **** and be misogynistic and Tweet communist support and as Twitter increasing censors those things people will move to other sites.
But Twitter might stay the "mainstream" one, like how The Simpsons is with comedy. Other shows influenced by it like Family Guy, Archer, American Dad, Rick and Morty, Futurama, South Park, Bojack Horseman, etc. are popular but they're not censored enough to be the "family" one.
So I think there could be rivals to Twitter in the future.