One thing to remember is that most people who pirate your game probably wouldn't have paid for it if that was their only option. Often times it's kids/teenagers who don't have much money anyway. Obviously AAA publishers feel that DRM increases sales to some extent, since they pay a lot of money to implement it, but for indie developers I think you're better off putting more time/money into marketing. Launching on Steam might be worth it for other reasons (discoverability on Itch.io is very low) but the DRM shouldn't be a big factor (besides as NTTP said Steam games can be pirated too).