This year they added an extended late antlerless season to 4A, 4D and 5A to help cut down on the deer numbers in those areas as adding additional tags was not getting the results they wanted.
If we didn't kill does we would end up with substantially less deer, that's what happened to the north central areas of PA and why they have so few deer today. They held off on issuing more doe tags back in the day, the deer destroyed the understory in those areas and when the area grew up it could no longer support the number of deer it used to.
Had they done more to control the population from the outset the deer would have had more food and been more plentiful as a result.