I presume they simply had to put our characters in somewhere ...
And Baldur's Gate is citty as good as any other, better even, since there is a lot of "exotic" people ...
If you want to play non-Baldurian, all you need to do is not picking [Baldurian] choices ... that sounds quite acceptable for me. O_o
I don't have citations to show but I have seen it mentioned that they do want to give custom characters special background stuff relating to being Baldurian. They certainly talk like being Baldurian is meant to mean something in particular. If that turns out not to be the case and you can just not choose the Baldurian choices, that's fine. Though if Wyll and Astarion and potentially other future companions can also choose those options, I will say that would be disappointing.
