Doesn’t have a question mark though, does it, so there! 😀
“Proper” etiquette just is. Convention and cultural/societal expectations are there for no apparent reason, but make a difference in particular company. “How do you do” done correctly, demonstrates a conformity, and if you like a background which embeds that social conformity. Of course, if you have no desire or need to conform to those standards, then say what you will. It’s the difference between “I wanna go toilit” and “I need to use the lavatory.”
Snobbery can be a destructive thing, and there’s nothing worse than faux sophistication al la Hyacinth Bucket, or even those coached in etiquette to an obvious degree, but occasionally it’s good (in my opinion) to set yourself and adhere to certain standards. Be yourself, but most importantly, allow others to do as they wish.
Do you eat pudding or desert? What about table manners….. how do you eat a bread roll with your soup?