There is probably a good story reason for this that has not been revealed yet. Also dialogue options, there are many unique ones for Lolth Sworn.
Also not all Drow are going to even want to be on the surface or wish to break stereotypes. By lumping them into only one type, it becomes assumed that they all want to be surface adventurers and "redeem" themselves. This unfortunately seems to be something many people try to force into DnD campaigns because they feel playing anything other than a Drizzt knockoff would be too "disruptive" or "negative" or whatever.
Would it be better for you if they added both types as two Elf subraces instead of a separate category? There could then still be the dialogue differences and possible story deviations.
