I'm so glad you asked!
Buying on itch.io:
- Supports creators - our default cut is 10%, but they can pick any.
- Lets you play the games you buy, DRM-free, whether you want to use our desktop client or not.
Many platforms out there are fighting for the "best Steam key reseller" title, which often means "the cheapest", and some are famously known for not caring whether said keys were acquired legitimately or not.
(Keep in mind that key reselling is something Valve allows because having more players now means more revenue later. If/when it stops being economically viable for them, they'll have no reason to keep allowing that. Those platforms might have to rethink their model then.)
As for itch.io, we let developers sell external keys as they see fit, but our main focus is building a complete, self-sufficient platform where they can upload, sell, market, and update their games, communicate with their player base, gather feedback for their next releases, etc.
That's arguably much harder, since we don't already own almost the entire market (Steam), we're not a spin-off of a hugely successful game studio (GOG from CD Projekt Red), we're not custom-built for a publisher to keep Steam's cut of the profits (Origin for EA, UPlay for Ubisoft), we're not running on venture capital (Humble), not owned by a retail giant (Twitch with Marketplace), and our willingness to help creators rather than squeeze out the most revenue has led us to decline a bunch of "opportunities" or practices others don't seem to have problems with.
It's working out okay though! We've been profitable for a while, and we're excited to keep adding features to the website and desktop client that benefit both creators and players.