Earlier quoted context omitted.
People have to prioritize their time. If they get messages from someone, they have to weigh responding to it against all of the other things they may be doing with their time (other messages, that ticket you’re working on, etc etc.) By just saying “Hey”, you’re leaving a message of unknown priority . You’re giving the other party zero information as to what you might want. If you say that to me, you’re saying “I need…
I dont think it is a problem with saying "hey" but when you say "hey" by itself. All the time I will say something like "hey" and then a followup message with a short question or asking how they are doing, etc etc. But for sure it is annoying when someone sends me a message that says "Hi" and then says nothing else until I respond
"Hi - remind me what time we're meeting" is fine. "Hi" is not :)