Well, there are a lot of people that play simple games like Solitaire, mines, Brain Age etc that are not social at all. And the so called "hardcore" also play online or locally with friends FPS, Sports, etc. So I don't agree at all.
I think the word "hardcore" was invented by experienced gamers to separate themselves from the new gamers, most of them in the range of 15-35. The problem with this "hardcore" is the way they look at the industry, where they look at themselves as the smartest and most important market, and ALL games should satisfy them. They don't or can't understand people may have different tastes than them, and if a game don't satisfy them they label it as Casual or Kiddy.
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