You collect coins. You then use those coins to get extra lives or buy things. Get used to it, because that's the way the world works.
Money has appeared in games for decades now with seminal games like Super Mario Bros. having players collect coins. Players must collect coins to get more lives — meaning, you get money or you die.
Adventure games like The Legend of Zelda and role-playing games like Final Fantasy allowed players to take in-game currency and buy things like swords and potions. There might be the occasional free lunch, but most of your in-game items are going to have to come out of your pocket so pony up the cashola!
Strategy games and simulators have rocks to mine (and destroy) and trees to cut down. And Animal Crossing features home loans. (Home loans!)
More recently, turned-based strategy game Greed Corp., released last month, is built on the entire concept of the annihilative power capitalism can have. Players must mine their tiles for cash that they can spend on weapons and robots to destroy rival corporations, and in turn, wreck the environment, leaving it in crumbling into bits.
Forget the industrial revolution. This is, for better or worse, 20th century capitalism: make money, eradicate the competition. The way the world works is just like this — not just in Greed Corp, but all around us. Greed might not be good, but it exists, even in video games.