What Valkenar said, for one, but the other is that I think a new leader that hasn't already been in Battle for 100+ hours is more likely to look negatively on a hero that hasn't logged in but once or twice the past month and give them the boot. Also, characters of an 'older guard' usually feel out of place with new leadership and an up-and-coming range and take that time to bow out.

Now, if I were leader, I'd boot the crap out of wafers, slacks, and incompetents, (especially if they have other active characters) but that's just me.