Dukeanumberone
It Wandered In From the Wastes
It is not the Brotherhoods job to help anyone in the wasteland. Their job is to collect, and sit on technology. They help people out willingly.
Per Maxson in FALLOUT 1 , he says there number one priority is to survive, make guns #2.
So if there survival in the CW was dependent on the local populace ( which to my knowledge is never mentioned other than recruits) then they would do something about it. But Lyons does list his own reasoning and some of it makes sense.