That is exactly why they don't want the "hello". They want to know what the question is before they socially commit to answering it immediately.

that's an unusual style of communication. You are coworkers. If you don't know the answer immediately, say it.

Consider too, that i might be blocked as long as i don't have an answer.

Then say that you're blocked and need the answer soon. Communicate what you need instead of making the person you're reaching out to guess.

That's exactly the problem, though. You're expecting prompt replies in an async communication medium. Ask your question and then they'll get to it when they have time. If they never reply when you do that then there's a larger issue, but that rarely ever happens. People expecting immediate replies in Slack is a big issue that leads to a lot of unneeded stress at work, and decreases everyone's productivity in the long run.

I dont expect an immediate reply, just within reasonable time. I i've made the experience that a question you ask upfront simply gets ignored and then forgotten.

When that happens to me, I'll give it a reasonable amount of time based on the importance of the question (which could be a few hours or a few days) and then gently prompt with "hey, sorry to bug you, wondering if you had a chance to look at my question?". That has never not worked out for me.

If it's such an emergency that it can't wait, then I can call them. But most of the things we think are emergencies aren't, and most things can wait longer than we think.

See, at least at the places I've worked, Slack is absolutely not an async communication channel. Some things are async, some need an answer now.

Most things that people think need an immediate answer actually don't.

Sounds like you're taking advantage of the politeness of others to foist an unwanted interaction on them.

no, just communicating with my coworkers.