there is something to be said for momentum and young kids that aren't typically used to travel
however there are football reasons as well
the crowd is screaming in a tight game when you are on the road and that makes it more difficult for your qb to make checks at the line scrimmage and communicate and get everyone on the same page so you are less likely to get into favorable plays at the line of scrimmage
so there are a few factors - usually though i think it is overblown - great teams usually have great home field atmospheres - those great teams when at home - not necessarily b/c of the atmosphere but b/c they are a great team - does it help, sure, but not near as much as some commentators would have you believe
