[keyringlight]

Isn't that a consequence of it being a fairly open platform and no certification gatekeeper before a developer can release/update their game? The platform isn't specifically steam or where mouse/keyboard is unavailable or inconvenient, it's generally what they think most of their target market will be using which is likely a generic windows desktop. I don't think developers or valve themselves would want to set up certification and enforcement to say "you must have X in your game otherwise you can't release on steam", especially for the wide range of categories of criteria you could possibly think of, and someone out there will want a way to do text input on their steering wheel for a driving simulator. PC gaming casts such a wide net it's likely an impossible task.