But not everyone follows our example, and that's really the point. (I'd probably edit to make it more clear, but that time has passed)
Same goes with sour. I love sour stuff and things I drink and eat that are perfect, you might find "objectively too sour", while it's really subjective.
If I go to a cafe and it’s done by an expresso machine then I get it with milk. As sometimes I can taste when they haven’t cleaned the machine in a while and it bothers me. Milk masks the bad beans or unclean machine.
When you use cheapo beans from Starbucks or the super market, it’s difficult to make good tasting black coffee. So making it with milk makes it drinkable.
And let me tell you, they aren't all bitter. If I did a blind taste test, I'd swear some of these were teas. Some are more of the taste I'd expect from black coffee either here or the US, sure. But wow, is there variety.
This is quite literally a matter of personal taste. There's nothing "objective" about it.
Bitter or acid are univerally recognized as objectionable. Sure as spice in another dish they can do something. But that's not how they work in coffee?
That isn't remotely true. If it were no one would eat dark chocolate or sour candy.
> But that's not how they work in coffee?
Also not true. While you might not personally appreciate it, coffee is far more complex than just "sour" and "bitter".