There are people willing to pay $80 for your game, $60, $40, $20, $10, and $5. You might be able get someone willing to pay $10 to pay $15 with good marketing, but you will never get them to pay $60. So when you’ve gone through most people willing to pay $60 and $40, you might as well go through the rest of the market. It doesn’t cost you that much more than you’re already spending on servers, so why not make that extra money.