I may be way off base, but let me lay out my logic. If I allow a buck to live during the rut he could hypothetically impregnate a doe and she could carry his future offspring.
Obviously, to make this logic work I would have to not kill any doe after the rut. This may sound a bit looney, but I have never heard anyone mention it. I know the doe wouldn't always produce a buck, but it could lead to a 50/50 chance, right? Plus, if the buck gets "busy"

with more than one doe my odds get even better.
Anyways, after the rut is over I could still nail the buck and feel confident I will be doing the same thing to his son in a few years. And yes, I have hada fewbeers tonight.
If this is just sounds moronic feel free to let me know.