Interesting topic---always seems to touch a nerve with some folks.
Hopefully no one enjoys a rout. There's no glory in lopsided victories.
As many above have already stated---can be used to get girls in that normally don't see a lot of playtime, let players try positions they don't usually start, or to work on some plays that need practice.
But there are some that say "never let up", or "it would embarrass the other team if we didn't play all out".
I know some parents that can't enjoy a game unless they are assured a big win, but where's the thrill in a game where the outcome is never in doubt? Personally, I relish a close, hard fought battle. It's no shame to lose a game if both sides played well.