I believe it's more about the individual deer's testosterone levels. The idea I've heard, and it makes some sense, is that a dominant buck just wont give up so long as there is a doe around to be bred. A buck still capable of breeding still has elevated testosterone levels and is likely to still have antlers.

I cant honestly say where I got this. If anyone knows of any scientific eveidence to either prove or disprove this theory, I'd like to hear about it.