I find bumps processes often dependent on the gate agent. Some just go through the motions, some go for least work, etc.

If plenty of vounteers, they will often not offer as much. However, the passenger always has the right to refuse the bump IF they decide they will not take the offer.

What gets me angry..... On overloaded flights, some agents dont even ask for vounteers until after boarding has started. That has resulted in them coming on plane and asking. Why dont they just get volunteers in advance when they know flight is overbooked, even if only by 1 or 2 people?

I usually try to stay a gate as long as possible on overbooked flights (and I have volunteered). I have seen where agent, rather than ask for those that volunteer, asks the last passenger(s) checking in if they would take the compensation and take a later flight. If I am nearby, I remind agent that I should be the one getting the compensation.