The Underdark consists of the Upperdark, Middledark, Lowerdark.
The geology of the Upperdark and the Middledark is super hostile. Based on Canon Lore books, the combination of disorienting tunnels, claustrophobia, stale air, extreme silence—drives you mad—, lack of food and potable water, disease, "living" rock and fungi that itself is poisonous, and then add on top of that the denizens of the Upperdark, that just get more wicked as your get deeper....
Yeah, it shouldn't be that difficult to get around in there!!
But seriously, even Canon Lore books describe how Sshmaath has human and Elvens living there, even as free beings, though are "kept in check" by the Ruling forces. So it isn't as if there is no connection between Sshmaath and the Surface.
Essentially it comes down to how Players treat the Upperdark and on-their-way-to-the Middledark, or Sshmaath (as that is our Server's only Drow city).
If Players treat the Upperdark as a metro line, and us it like a daily commute, that is what it will become. If DMs also support this via action or inaction, then as well, it will become solidified in the consciousness of the Server, and it will become a RP-light background to whatever OOC desires are the flavor of the day, of the individual.
However...if Players treated it AS difficult, scary, violent, awful, worthy of the legends of Lore and did not abuse its existence from OOC motivations, and, the DMs also made sure that through RP interactions and Events, the entire Underdark that is in-game is not experienced as weak mechanical challenge but something that is more-on-the-chance-of-failure-than-success...for this is Canon Lore..., then possibly, the stories would become richer.
Personally, I don't know why the Upperdark wasn't made one of the most difficult regions on the Server, both mechanically and RP-wise, as that is how it is in Canon Lore.
The Underdark is harsh, one of the harshest environments on Toril, often compared to conditions of difficulty equal to the harshest deserts on the Surface. If you don't believe me, I suggest you go read your copy of Underdark, or even,
preview it here (if you don't own it).
Check out for yourself just how crazy insane it would be to, not only travel there from the Surface, but...get the hellz out of it, alive!!
Then decide if you are going to be a RP'er that upholds that Lore, or not.