Yes, because that's the Duergars' creative origin as a D&D species. I mean generally species in D&D have become more accessible/likeable and grey. In the beginning, orcs were generally evil. By the mid-90s, even goblins were available as a playable race. Duergar on the surface are of course possible. Drow are described as slowly losing their Underdark-related special abilities, like levitation, and their aversion to bright lights when they spend too much time on the surface. However, there are no rules describing such a process for Duergar which would leave them at a disadvantage unless you give them a house rule. Duergar living on the surface must have been a thing with BG2 which I unfortunately never played, then.
The Complete Book of Dwarves, which I think introduced Duergar as a playable race, states any bright light gives them disadvantages. (Fact check: nope, it was indeed AD&D 1st Edition's Unearthed Arcana by Gary Gygax in 1985 - but similar restrictions).
Duergar are adversely affected by bright light such as sunlight or a continual light spell. They are not affected by the light of torches, lanterns, magic weapons, light or faerie fire.
Affected by bright light, his enhanced ability to gain surprise is negated. Dexterity is reduced by -2 and hit rolls are made at a -2 penalty.
In situations where a duergar is in darkness but his opponents are in bright light, his Dexterity and surprise advantages are unaffected, but he suffers a -1 penalty to his attack rolls.
Other dwarves distrust duergar and react to them at -3 penalty.
