“You all” or “you both” or “you”or “you guys” seems less icky, like they don’t view you as a couple saying “you two”, like you are up to no good.
I don’t know the terminology, but I think it’s because it’s a direct indirect. It’s like saying, “you there” instead of referring by name or using like, “excuse me sir/ma’am” or even skipping the direct call out altogether and saying, “could I get some help”
Basically it skips all formal addressing and is like using slang to people unfamiliar. If you are familiar then it’s rude because you should know their names. I think the main time something like that is used is in an informal setting where nobody is actually familiar with each other, or in a scenario where immediate direction is required without prior familiarity.
