Social etiquette is strange

I think its common knowledge that its polite to greet people but when you're walking in a populated area its kinda hard to go greet everyone one by one so its allowed forw to just carry on walking oblivious to all the other bodies.

So now its all quiet back street stuff and no matter what kinda person you are, whether you're a hoodrat or a jock or a nerd or whatever, if you're in a one on one situation with someone you have to give some form of salutations whether its a nod of the head or a whats up or a flicking of the bird, anything.

So im walkin past this guy and He's all OG Whiteboy in his baggy school pants and cowboy walk, that walk is actually used to keep the pants up regardless of the belt thats there. So im walking towards homie and i do a quick assessment. Im positive he does the same as he comes towards me and We're both kinda glancing at the gap growin smaller between us and making our assumptions and judgements until We're like in front of each other and both of us simultaneously give a single nod and carry on with our lives. Somethin similar just happened now as i was writing this i came to a ye olde gentleman reading his post and a quick hello and one is off.

Do girls do this sorta thing or are they too busy sussing each other out? Strange cats those...