Wow, do people on here have short attention spans or do they really need the answer stamped on paper for them?
If respawn times were quick what reason would people have to take the revive skill? If the auto respawn time was quick how would you have time to flip through your loadouts to switch before the computer forces you back?
The longer respawn times were at least thought through by the developers; in my opinion, I would have made the respawn times even longer such as 1-2 minutes to truly penalize a person or team for losing a member and not trying to revive that person or not having a medic.
I hate instant respawns in Objective game modes. You have no real penalty for dying if you can just jump back in the action. For FFA and TDM modes I'm fine with instant respawns though. Respawn timers help the better team/players win, which is how it should be.