I just attended two basic skills shows.
Along somewhat the same lines as what icedancer said, clapping is very important for the parents, friends, and fans, because it makes them feel supportive of their kids, friends, and favorite athletes.
It is important to most of the kids and other athletes too, whether they hear it or not, because it shows them they have the parents' and friends' attention and approval.
I.E., I see no reason to change the applause.
I think yelling and screaming at concerts is
counter-productive - but it seems to be very important to some fans, and for some musicians.
I'll never understand sports fans who yell and scream at their TVs while watching a game.