Even for larger realms, monsters can spell death. The Lurian lands (which are allied and helping each other out, might as well be one realm for dealing with monster purposes) have been hit with hordes that are at least two, possibly three times the combined realm's CS in the past two weeks, and we've got another fifteen thousand surrounding us right now with some moving in.
Besides, SA can be reasoned with. It's only a problem for those who want it to be a problem, in which case it's not a fear as a desire.