Why should they? Underdark characters bring a lot of interesting RP to the table.
Plenty of people do this, not just drow. And there's no 'silly surface laws' in the north, where drow would be.3. the general 'safe' area that has been abused to hell and back again by UD is the shrine of Eldath in the Reaching Woods, where veiled threats, taunts, etc are made because its a shrine to peace and therefor no blood should be shed there, so people use it to troll and try to force a reaction from other people. Making more 'safe' areas for UD people will likely only increase that. "I'm Evil, I'm a drow, I taunt you, but because you follow your silly surface laws, you can't do anything about it Blows Razzberries" isn't exactly compelling RP, and I fear that is what the 'safe' areas will turn into, "I am going to be mean and insulting as an evil character, and you can't touch me, because I will just teleport out after saying all these horrible things and spreading horrible lies about people and just slip away out of your reach." Just gets annoying rather then compelling.
People already do this. Also IMO, paladins should be the ones showing up in Soubar in cloak and hood, not drow. Drow fit the aesthetic and theme of Soubar, knights in shining armor don't, yet they keep coming by all the same.Plus if you are evil and want to make deals with other evil factions, taking away the clandestine meetings in deep caves, just to be able to show up to the bar in sobar and talk about such plots openly is sort of 'meh' as well.
The north is not Baldur's Gate. Soubar has a mindflayer vendor, werewolves, wererats. Uruk Lurra is black orcs and mountain orcs. Corm Orp and Darkhold are Zhentarim. There is no reason why drow should be any more KOS in the north than anyone else living there. Heck, like I said above, good-aligned PCs should be more KOS than drow in most of the north.5. If you are choosing a Monster Race to play, and you are by basically playing any UD character that goes to the surface, don't be surprised at your lack of RP. The same should be said of Surfacer's going to the UD for RP, you are the monster down there, they are the residents.
The more we can do to make the north an openly dark-aligned area, the better.
Obviously, there's more work to be done for that. The south needs more epic areas to encourage good-aligned PCs to do their hunting on server 1. The north needs more leveling areas to make it easier for newbie team evil to level up efficiently. But that's a development thing, not a rules thing. I think, now that we have a two-server solution in place, we should really be take advantage of the culture that's already been developing where north is the realm of team evil and south is the realm of team good.
As I posted on discord, it should IMO work like this:
Underdark (surfacers KOS) -- Upperdark (no KOS, or global KOS) -- Surface, North (no KOS, or global KOS) -- Surface, South (underdarkers KOS)
Then ensure both sides have plenty of necessary content. Heck, I wouldn't mind even just copy pasting dungeons. There's no reason every troll cave has to have a completely different layout. It's not like immersion would be broken any more than it already is with the 'I know exactly where everything is and kill the chieftan on a daily basis!'.