Not all American Indian societies were kind toward captives. In the Pacific Northwest, the locals had a well-defined tradition of slavery which they extended toward captives they took in war and most notoriously, toward castaways and other people who shipwrecked on their shores, as evidenced by American, English, and Japanese accounts. They're pretty much a raider society as OP describes. It wasn't so bad to be a slave there, if you compare it to the Caribbean/US South, since they did the same work the commoners did, but slaves had no rights and thus could be married to whoever their owner decided, raped when their owner wanted (for women), traded to a new master if required, or sacrificed when needed. Commoners were not subject to this. Slaves had no hope of rising far in society. If a slave had no useful talents (unlike the accounts of some people taken as slaves by these American Indians), they'd likely not have a good life. While there's a lot worse (again, Transatlantic slave trade, blackbirding, etc. existed), being a slave to these Indians would not be a pleasant experience.