re: A rule I never understood and would like to see changed

It's not considered a "fumble" in the same sense that a, well, an actual fumble is considered a fumble. Yeah, it's a live ball, but, since it was in play, it was a live ball before that, too. It just couldn't be advanced by the kicking team by any means other than the initial kick.

Punt rules are different from normal scrimmage rules for a good reason -- the circumstances of a punt aren't analogous to the circumstances of normal scrimmage. The receiving team is being asked to either field the ball or take their chances on the bounce. If they could stop the ball dead just by touching it, there would be no incentive to go for the fair catch (and potentially muff it.) And if you declare the ball dead as soon as it's touched, then how would a punt return work? It's a dead ball from the moment it's caught.