People who don’t say “hello” back to strangers, what are you thinking?

If I did not hear or recognize that I was being addressed, then it could be anything. One must always make allowances for this.

As for minimal or no responses to random greetings, it is usually because:

  • I get greeted a lot by strangers and I’m not a public figure.

  • In certain contexts, there are people harassing others randomly and acknowledging them gives them an in. This is a security concern in some contexts.

  • Being in public is not an invitation to any social interaction: it has to be reciprocal.

  • There is something more important on my mind which requires my attention rather than a social nicety that has no meaning. If one thinks one is the most important thing in a random person’s life, then one has a problem.