It's a misuse of tools indeed. It's something to do on the phone, not in a (supposedly) asynchronous communication tool. But hey, some people even use email synchronously.
I tried to punish the naked hello senders, by simply not responding at all. If you can't be bothered to tell me why you need me, I can't be bothered to respond.
Unfortunately, empathy broke it. I work with a lot of remote workers in India. They make long hours and I know they need something from me, I just don't know what. By intentionally not responding, I feel bad about effectively sabotaging progress.