As others said my impression was always that Lolth Sworn is shorthand for the normal Drow from previous editions (evil Lolth worshippers) to differentiate them from the recently introduced good drow because it was decided to not have always evil races anymore.
Good drow existed since the second edition. But their numbers are still very low. Ppl might got used to tieflings somewhat, but vast majority still will be very warried, if they will see drow.
