I don't get why it's so frowned upon, period.
I'm white, have lived here in the US since birth (never even traveled overseas), and I spit.
Granted, I don't practice it like a backwater hick who'll do it just about anywhere... I would consider myself cultured and "with manners," but sometimes some nasty crap has to get expelled. I think I just have bad sinuses, not terrible but not perfect. I'll hack up some throat-clogging crap. What do you want me to do, wait forever with the feeling a frog is trapped in my throat, until a moment I can enter a bathroom or something?
I try and be as discreet as possible, and I usually aim for grass whenever practical if outdoors. I won't necessarily do it when surrounded by 1000 people, or when all eyes are on me for whatever reason, but the moment it seems "clear" I'll give it a hack. If it's outside and mostly grass, I don't usually refrain except in specific circumstances.
I don't understand why we have the strangest stigmas and social "no-no's." We can't just gracefully move beyond being animals into some kind of enlightened state of being. We eat, we shit, we piss, we fart, we burp, we cough, we sneeze, we hack up nasty sinus drainage, and hell while we're at it, let's not forget we fuck... and I'm sure I'm forgetting a few things.
Why even pay it any attention? We have certain bodily functions that can only be repressed to a certain degree. We've only made it more awkward to do that which we have always done, and which we will forever do. Why make it something that even needs to be addressed?
Aside from certain anomalies (very specific situations), I've personally moved beyond even addressing most burps, sneezes, and farts. Why even say anything? Have we not moved beyond the point where we think such functions are the body's way of purging evil and demons from itself?
Sure, in a stuffy meeting, it's not really a good idea to do any of that. That's a moment we're playing the enlightened being role, where we more than an intelligent animal and doing, supposedly, very important things... but when we're just going about daily activities, who the hell cares? If you do care, why the hell do you care?