I watch a few let's plays a year, of games that I'm too lazy to play myself.
Oh, just for the record, I follow one, DGR, because the host is charismatic and play something I'm not going to (custom Mario Maker levels etc.). Sometimes I watch those compilations of reactions to horror games etc. because they're really funny.
Not really, never understood their attraction if I'm honest. Watching other people play is very, very far down on my list of interests. I do sometimes use visual guides if I'm stuck in some game, finding an obscure item or hard secret location.