Spambusters is a good idea under the right circumstances. But this is a rare occurence. So, Admin have to think about training, supervising, advertising & reallocating as people leave, shifts, etc. And they need them most when they are not around which means American, Canadian & Australian/NZ members mostly.
It's all extra work for them. They may be volunteers but it's still a time commitment and they all work as far as I know their time is more precious to them than many of us.
Once the keywords are in place, it's just a hassle deleting members and their mess but they have the situation controlled away from the forum. They've had to capture certain words before e.g. suicide...and Lord Voldermort of course
I think they had one of these a while back, it's just this one is more persistent. If so, that's two. Is it worth extending roles that have to be managed for that?
If Admin need help for the rest of the work they do, I'm sure they will approach people they believe suitable as they have before when Admin's left.