I care because I’m curious. You clearly care otherwise you would have ignored the thread. Why do you care?
No I do not care. I simply don't (also this thread is not about sales, its about hours played in the game and other game play stats which I think are interesting). I just want to know why the average Joe gamer actually "cares" about sales numbers. IMO, saying you care about something like sales would mean you have skin in the game or are concerned for the outcome for whatever reason.
Stating you are curious about sales is one thing. That does not attach emotion or concern with the outcome. Saying you care, is the opposite.
I care about the sales for the company I work for. I have a vested interest, due the sales we make directly impact my job. I care about the sales of my various investments and such. I really do not care about a game's sales. Sure, I might get concerned if it was a game that I really enjoyed and I want a sequel for it or something like that. But that is because I want to play the game more, not to use the sales numbers as some talking point about the console/game or anything like that.
I see people all the time arguing on here, using units sold as some sort of end all be all metric of a game. Great games sell small amounts all the time. There have also been many terrible games that have sold large amount of numbers. The number sold does not necessary reflect how good a game is.
My point is, unless you have a vested interest in the game, why "care" about the sales numbers?