You ever notice Drew Brees never calls an audible? Compare that to an offense the likes of the Colts and Manning appears to be audibling almost every single play (even though he obviously isn't). The Saints plays are designed so cleverly that we don't ever need to audible as the defense has no idea where the Saints are going with the ball on any single play, no matter what the formation. Pretty amazing.
I guess you don't need options before the snap when you have so many options after the snap. Plus Brees has always been know for dumping off the pass if they are caught with less blockers than rushers. How many times do QB's audible into a worse situation? It seems to happen more often than not.