Main Base for both Teams

The Main Base for both Teams we all know cannot be gone into by the opposing Team,,  WHY?  are these Red Zones not considered No Fire Zones (cannot shoot out of or into)?  On certain Maps the area was expanded due to aircraft maneuvering and I agree but in instances like Operation Firestorm the Mountain range next to the North can be driven on by Tanks/Bradley and Snipers have found a Very High Nest to engage the opposing Team, this was implemented in previous Battlefield Titles, while even if individual soldier spawn protection (as with previous titles) will not reduce the Issue entirely, but every improvement will keep players coming back to Battlefield.