4. It Keeps You Interested
Well, that's the marketing idea that keeps MMORPGs companies alive. You jump into a game, you get fascinated by the game and by its player versus player combat (which is, by the way, only really fun when you reach the level cap), and then you spend literally countless of hours to get your character to that respective level just to see your face owned by dudes who invested more money into that game than you. By the time you do that, you really don't care anymore. You almost finished the game, and you probably already bought the full year's membership to the game, and you are going to play it just to convince yourself that you didn't waste 100 bucks for only 25% of what you could get from it. The same applies to any other competitive game. You enter PVP, you get your ass handed, you rage a lot, then you come back, win some games, get your hopes up and lose again.