I don't think Reddit is mentioned enough as a reason, but the focused Reddit communities are much better than SO for finding answers and asking questions.

This isn't to say that Reddit doesn't have its own issues and overzealous moderators, but I would hit r/sysadmin for info on an outage or bug before I thought of SO.

I would also throw Slack in with Discord. A lot of my vendors have public Slack instances where I can ask the same question with a much better audience.