What's funny to me is that the amount of "same here", "+1" comments are still prominent even if GitHub introduced an emoji system. It's like most people intentionally don't want to use that.
(Just kidding.) Some of it is unawareness of the 'subscribe' button I believe, occasionally you'll see someone tell people to cut it out and someone else will reply to the effect of wanting to know when it's fixed etc. But it's also just lazy participation, echoing an IRL conversation I suppose, that you see anywhere - replied instead of up votes on Reddit and to a slightly lesser extent here for example.
