So your out on the wastes and you get attacked by let's say 3 raiders.
By luck, skill, expireince, or outside intervention you kill 2 and knock out the third. Great fo you, now you get to kill her in cold blood.
Oh, WAIT!!!! If you had been a slaver, you could have taken her for slave, sold her, and kept the monery.... Except you didn't become a slaver.
So my proposal is.... You CAN use ropes to bind CRIMINALS (otehr than trappers, maybe) and sell them to NCR or any other CITY (not metger or whatever) as "bounties" on them. Same bounties as you get for slaves, applies only to criminals (so nothing for kids), no karma hit but no gain either.
Just somethign to consider..... I mean, in the real world of fallout, that's exactly what would happen. If you were lucky enough to survive an ancounter with raiders you could take them to the local sheriff and collect a bounty on them, but it wouldn't be a great trade to get into- too high risk.