Steam Input for use with my steam controller and playstation controller for gyro controls. Particularly love the dual touchpads for movement and camera controls and extra click inputs over a single joystick click. I can't deal with default control schemes anymore when it comes to controllers after becoming reliant on the amount of customization Steam Input provides, since it goes beyond a simple remapping with layers, modeshifts, chords, touch menus, action sets, etc.

Linux support that reduces need to fiddle around with settings and mess with lutris type tools and more devs putting in the time to try to be Steam Deck certified. Even when it doesn't run well on the Deck for more demanding titles there is still benefit for more powerful systems and future Steam Deck follow up.

Existence of Steam forums and guides has come in useful for help and has popped up on search results that I wasn't able to find on pcgamingwiki, so reddit isn't the main place I need to rely on. Been a way to also try to reach devs without having to use reddit or twitter.

Steam workshop. I do use nexusmods, moddb, etc. But, sometimes just having it integrated into Steam makes it convenient.

Other launchers are more like comparing a dumbphone versus a smartphone where if all someone wants to do is make calls and text that is fine, but for those that have become accustomed to Steam launcher features beyond launching games there needs to be more done by competitors. Having to use stuff like GLOSSI to try and utilize Steam Input when using third party launchers, or have to fall back to syncthing to try and sync saves from other launchers when using Steam Deck just makes the lack of Linux and custom controller support apparent.

Which of these features do you actually use and why wouldn’t you want the devs to make more money so they can produce more games that you, as a user, can play?

In case the question wasn't targeted at them specifically: Play games on Linux and making sure the actual monopoly of Windows gets broken. Parts of Valve's revenue goes into open source development, meaning that in the end more developers get paid: https://www.phoronix.com/news/Valve-Upstream-Everything-OSS

If game developers think the cut is too high, I'd be thrilled to see them distribute their games directly through Flathub: https://docs.flathub.org/docs/for-app-authors/submission/