Briggs "For all we know" Deep Elves love music deeply and Deep Gnomes sing instead of talking. Fact is we don't have an explanation of why there are no Deep Race options for Bard, both in-lore or outside of it.
Cutting an entire section of the game off from any form of music could be cool with the right lore, but we don't have that, instead we have plenty of Fantasy history that presents music as a thing for the nasty creatures inhabiting the deep places, starting with "drums, drums in the deep".
It's weird to not have a single Deep Race option without explanation, that's all.
It's not as if the game is ruined without it though.
