It's what gives US chocolate the "vomit/bile" taste uncommon in other chocolate. I am guessing it becomes acquired or unnoticeable taste for people who eat it a lot but man is it a shock if you usually eat chocolate without it!

I have no idea why they use it, but I can think of one really good reason why they shouldn't, your product probably shouldn't have "hints of vomit" in its flavour profile.

I mean it's also in cheese. People just aren't used to the weird tang, and I don't blame them. I can tolerate it but Hershey's isn't exactly my favorite haha