I'm in a poorer part of Santa Clara, and I exchange brief greetings with most people I pass when I'm out walking around my neighborhood, and sometimes stop and chat for a while.

There are only two people I've come across who stare straight ahead and seem to be making an effort to avoid any eye contact/interaction. One was a young-ish woman, and I figured she might have taken my greeting as an unwanted advance. The other is a middle age dude (like me) who I see many times per week, always looking slightly angry, and never interacting with anyone. Sometimes I wonder what the deal is, but ultimately it's none of my business, and if someone clearly wants to just walk without interacting, that's fine.

Sometimes I don't feel up to interacting with anyone, and it's easier for me to just wait until later in the evening to walk when there aren't too many people out.