I always field dress my deer where they die, or as close as practical. I've been known to drag the deer 20-30 yards to a clear spot to make the task easier. Otherwise there is no good reason NOT to gut them ASAP. The guts are where 90% of the bacteria responsible for decomposition and spoilage are at the time of death, so removing them ASAP reduces the rate of decomp significantly. Also, removing the entrails and opening the carcass greatly speeds the cooling of the carcass (and allows you to pack the carcass with ice if necessary), which also preserves the meat. Thirdly, I don't know about you, but since the guts constitute roughly 1/3 the live weight of the deer, I'd rather remove them and lighten the carcass than drag the whole weight of the deer.

Mike