Given how easy it is for posts to get deleted there, it almost isn’t necessary but I guess it could be useful if someone is constantly looking for you, and bugging you there.
I haven’t yet had need for it on YouTube though.
I don’t know, I almost never use block features on sites, and I’ve been unfairly blocked by several people (for the crime of disagreeing about something, usually about in the Sonic series usually, I can’t stand people abusing the block feature) so I’m not very block trigger-happy.
I kinda have the mindset that I’d rather someone say something to my face behind my back, but I usually ignore some aggressive people and they just go away.