LinkedIn. Needed to find a job in my domain. Also people often talk about their posts. It makes people really happy when I like a post they talked about to me. When I don’t have a job daily.
Tweeter for some very specific events. Something like two weeks a year
Hacker news when I do not have anything to do at work. I say to myself that it is to stay up to date and sometimes I can find nice blogs. I would say something like once a month.
I’m unsure, but I’m betting a lot of marketing, HR, and upper level stuff is mainly through LinkedIn. Programmers and coding probably go through other sites. I know Indeed does a lot of office jobs, others are good for gig work.