I see why you'd find doing that with a Drow or Deep gnome to be more reasonable, but my issue is still that, unless you have a particular backstory, they still don't *really* know what they're jumping into. We don't know where our character was taken from. They could from anywhere.
The beauty of a custom character is that we can give them a particular back story that makes sense of it

. Of course, it’s possible that something in the full campaign will come along that contradicts it and means it needs to be tweaked, but I still like to have a good idea of who I think my character was before they were kidnapped. And I’m not above a bit of meta-gaming to create a character who I think will be able to do something different and interesting once I know the outline of the story and what my options are!