boxing question

[Doosh]

Howdy, quick and presumably stupid question on boxing wager. Looking at the Toney-Peter fight, Pinny has the following:

Toney by decision +191
Peter by decision +201
Draw +1656

Over 11.5 rounds -231

It seems to me (as someone who has never wagered on boxing) that the combination of fighters by decision and draw should be fairly close to the over. But it's not. Is there an outcome I'm missing, or is it that likely that something will happen in the second half of the 12th round that will keep it from going to a decision/draw?