Thinking about that a bit, it would probably be possible, but there would be downsides that might not make it worth it. For example, supporting people on the low side of hardware specs complaining that X game/software/etc isn't working well enough. Conversely, other people on the same hardware might not have an issue with it. (different levels of "acceptable" for different people)

Not sure it'd be worth the effort (any time soon). There are other much simpler things Valve needs to fix first in order to increase sales. :)