I am not advocating or praising this behavior; I was definitely going through my prima donna phase.
Later I became very timid about talking to people because the company culture was "if I have my headphones on, please don't interrupt me" but everyone had headphones on all the time because the office was a nightmare of noise and distraction.
The ubiquitous slack (or equivalent) channel has a lot of downsides, but when weighed against the alternatives, I think I like it the best. But I'm very conscious of the fact that not everybody's brain has the same attention system. I think that's one of the reasons this little device has generated so many strongly worded comments. It's probably neither the most rude thing ever nor the most helpful thing ever. What would be great for productivity and happiness would be if we could find a way not to force everyone to try to work under the same environmental constraints. (Aspirational: I don't know how to do this.)