This comes up from time to time on HN. Humans aren't machines. As self-important and busy as you think you are, why not take a beat and respond with 'Hey' and ask them how they are.

Humans are more than just social creatures - we actually NEED social interaction to stay healthy. Remote work is hard enough. Being alone in a room for days is hard enough. Don't be afraid to remove the stick from your behind and add a little social padding to your conversations. It's good for you, and it's good for the person this site is telling you to get cranky at.