If you're in a small town where everyone says hello to everyone else, or in a small enclave in a big city (like Breezy Point), then a man saying "hello" to a woman is just one person saying "hello" to another person.
That's not what is happening in these instances. I can easily walk past 500 people on my way to work in the morning, and that's just a few blocks. If I said hello to every person in the morning, I'd never make it to work.
As you noted: These guys are not saying hello to a neighbor, they're hitting on a random female, at any time of day or night. What is polite and normal in Smallville is a sexual advance in The Big City.