Imagine if SCP made you download every single nightly build, media tweak, revision, upgrade, downgrade, ship fix, effect patch and overwrote your FS2/data folder every time.
That's how annoying I find steam.
It'd probably cut down on a lot of the tech support threads... 
No it wouldn't. You would end up with MORE because of people getting errors because the newest build broke something. Not all builds are as backwards compatible as they would seem. For one, I remember the AI change back to retail behavior
severely messing up bomber ai resulting in a number of missions made with the "bugged" AI in mind basically unplayable. Also, since they're pushing for integration of INF builds, all your old pilot files will "disappear" (the game reads INF pilots from a different directory). You wouldn't hear the end of it.
Forced updating is BAD. It only helps n00bs, if that, and could potentially punish people that actually know what they're doing (ie. testing an older version to see if the chnage resulted in bugs, etc).
