You don't have to use Steam keys to sell a game on Steam. Steam only issues those keys if you request them -- you only need them if you're selling your game som

You don't have to use Steam keys to sell a game on Steam. Steam only issues those keys if you request them -- you only need them if you're selling your game somewhere other than Steam (or doing something like fulfilling Kickstarter preorders). If you don't request any keys, that just means that your game is only selling through the Steam store.