Game developers hire economists and psychologists to run experiments on the precise ways they need to design their games to make people feel like they need skins and other cosmetics and spend money on them. The games are designed to nudge people into associating having good skins with being good at the game and having the default skins with being bad at the game, and to make people want the new skins and feel bad for not having them. Furthermore, they don't really make money on the average person who either doesn't spend money on loot crates or maybe spends a bit of money every now and then- the real money makers are a tiny percentage of players who have some bizarre compulsion to spend absurd amounts of money on this stuff. These are known as "whales" and a lot of them have legitimate psychological issues that cause them to be like this or they're like Saudi nobility who just have absurd amounts of money and don't give a shit about blowing it on fake video game stuff.