Not sure how you came to this conclusion. I'm perfectly familiar with the Forgotten Realms and drow.
I'm also answering your other post as well. Duergar are the ones who are known for their slavery, they actually work their slaves to death. Drow do have slaves but they enslave mostly weak minded creatures such as the goblinoid races. According to the Drow of the Underdark guide from second edition drow only value human slaves when they have no magic or no fighting ability. They are not stupid nor are they murdering berserkers who all do these unpredictable things all the time.
Their hatred of surface elves has been around a long time and has been part of many novels and supplements.
If you want to know more about drow don't hesitate to ask.
What made me come to that conclusion is your inability to see drow as taking slaves of surface dwellers up to and including elves as somehow hard to justify. It isn't.
Why would I ask someone that thinks drow don't enslave as much as the Duergar about drow? They most certainly do. The hate menial work themselves. Goblinoids make poor craftsmen.
Here is an excerpt from
Drow of the Underdark:
"Humans make some of the best slaves, but they are also among the most difficult to control and frequently require execution before they can be worked to death."
Drow enslave Duergar, aboleth, illithid, just about anyone they can enslave. It is only the ability of the individual to resist enslavement that stops the drow.
They rarely enslave elves since they hate them so much. Yet they do sometimes enslave them as torture pets. They love to sacrifice them to Lolth.
I fail to see how someone that knows about Forgotten Realms drow would somehow think starting off as captives would be unusual for drow. It is very easy to justify why the drow might take any party captive. I'll include a last excerpt to emphasize my point:
Even though the drow are willing to take slaves from anywhere, they
do not go out of their way to take prisoners from these surface
races, as they do from those who dwell in the depths.
If some
are foolish enough to wander below, or if they get in the way
of a drow surface raid, then yes, they’ll find themselves spitted
on a drow blade, strapped to an altar of Lolth, or wearing the
brand of a drow owner—but for the most part, the drow have
more important concerns than what these foolish creatures are
doing hundreds and thousands of feet above them.
It's pretty easy to justify drow taking captives of surface races, especially some weak, starting off PCs that happen to get in their way. It's not a questionable start or anything of the kind. It's a very easy to incorporate start. The PCs happen to have been seen as valuable by someone in the raiding party that wants to keep them alive to enslave them. I would have plenty of fun with the original group Rema named. You can make that group burn with hate to avenge themselves against the drow.
