Imagine the "user experience" of accidentally buying a $999 app, then returning it. Feeling stupid, even if it's well deserved, just tends to distract from the user experience.
And for the onlookers not buying the app, it's bad PR for Apple as well. Yes, it's a restrictive gated community. Yes, the lack of freedom sucks. But some people are willing to play along to be taken care of by Steve & co.
So are you saying that companies in general should never give refunds, because there is a faint chance that there will be more refunds than purchases (which seems logically impossible, btw.)?
I see. Still, "I am rich" was sold 5 times and one person was a candidate for a refund. I would be happy with those sales (4000$ after the refund), given the short amount of time.