I have quite a few co-workers who when they send a message, will send a greeting and literally will not say anything else until you greet them back. Some even repeat their greeting multiple times, and one even complained that I had seen their message but had not replied. Sometimes when doing multiple things at a time, I don't see the messages or respond back right away. For one co-worker who was really bad about this, I had explained I may not see their message right away and asked them to let me know how I can help them and I'd respond when I could but they are still doing the exact same thing.
I don't want to make a huge deal out of it, but we're wasting time not just communicating and I think it's because they're treating it like a face to face conversation where if you don't greet them back, they can't say anything else. Is there something more to this behavior that I'm not understanding? We have asynchronous chat for this reason, I don't want to have to open the chat to say hello to my coworkers any time they need something.