How is it mind boggling? It's almost as if you people have never interacted with real people before. Have you never played a friendly match of some sport before? Some people play [insert any sport/game here] to relax and talk about their day with their friends. Others will invest much more time and energy, play on gaming monitors, communicate using military jargon, use paddles, a gaming headset, keep up to date with all patches, watch strat videos, use exclusively meta load-outs, jump/drop-shot, join clans, reach max level within a few days, exploit glitches, etc. Let's not pretend like there isn't a difference playing for fun vs to win a million dollars.

So no, there's nothing wrong with that, and I won't get mad when I run into one, but I will call him a sweat, because that's exactly what he is, and why the word exists.