As the WBOS put it themselves - they are not farmers. They need to eat too, and buying ammunition from the wastes can save the scribes/paladins from having to do it, and let them work on more important things. Estabilishing a good supply line is essential for survival.
Now lets think about this rationaly - Who is going to be better at establishing a the opportunity to trade for supplies, a stuck up group that wants nothing to do with the world, or a bunch of folk who are willing to go out of their way a little to defend the guy who sells the food and ammo?
I dont have a problem with the EBOS' going a little do gooder, to me it just makes logical sense - you don't crap where you eat, you make sure that where you eat is nice an clean, so you're less likely to get sick. Whats wrong with protecting that which is doing good by you?
I'd rather be in the EBOS. They've confronted the economic reality of their situation and have had no problem adapting to it - even if it means there is a little bit of a cost in having to do downgrade the priority of techhunting for techhunting's sake.