Uhhhh...yeah. Even if you really wanted to let your opponent return to the stage so you could attempt to KO him/her by launching him/her from the stage, you're only limiting yourself and making the match tougher for yourself if you don't edgeguard. For all you know, your opponent could just come back up and pull off the greatest comeback to take your last stock, whereas you would've taken their last stock had you edgeguarded.
And let's say you're good enough that you don't need to edgeguard against your current opponent. It's still just cocky and stupid, because it's not like that's going to work against everyone you play with.
How could anyone not want to edgeguard? It's just silly. Don't you think they'd do the exact same thing in traditional fighters if getting out of the ring didn't result in an instant KO (if, for example, you got a KO after being out of the ring for 7 seconds)? You want to beat your opponent. You don't want to do anything that will make your opponent's match easier. Especially in Brawl, where recovery is a lot easier than in either of the two previous games.
And let's say you're good enough that you don't need to edgeguard against your current opponent. It's still just cocky and stupid, because it's not like that's going to work against everyone you play with.
How could anyone not want to edgeguard? It's just silly. Don't you think they'd do the exact same thing in traditional fighters if getting out of the ring didn't result in an instant KO (if, for example, you got a KO after being out of the ring for 7 seconds)? You want to beat your opponent. You don't want to do anything that will make your opponent's match easier. Especially in Brawl, where recovery is a lot easier than in either of the two previous games.