I think development is a profession where it is not obvious when you are interruptible. In fact one of the best manager I had outright ask me "are you interruptible?", because she doesn't know if I am deep into a complex problem or just cleaning up stuff or waiting for my code to compile.
Manual labor also require focus, but when you are occupied tends to be obvious. If you are under a car, messing around with a tool in your hand, everyone knows it is not the best time to interrupt you. In safety-critical jobs, like in the case of pilots, there are mandatory protocols that explicitly forbit interruptions during critical moments.
People usually know enough not to barge in when the manager is having an talk with his higher up or when the salesman is negotiating with a customer unless it really is urgent.
But programmers just stare at the screen all day, and most of the work happens in their head, so how do you know if they can be interrupted or not. Bad managers assume "always", because themselves only stare at the screen during their "off" time, so they assume programmers are always "off".
I'm a mathematician. I spend a lot of time staring into space and mumbling to myself. Sometimes, though, when I'm just zoned out, my wife would ask: "Are you working on something?"
At a prior job we actually little LED RGB light tabs that would stick on our monitors, and set them to red or green to indicate exactly this. Uptake and responses were somewhat mixed, but it was nice to have an explicit signal, beyond just putting my headphones on, that I was not going to be welcoming of interruptions for the next few hours.
At the time we were in a pretty cramped office in a co-working space, so I appreciated anything that could help cut down on distractions even a little.
I have problems building habits going out of deep work. It's like the problem is less getting dumped from my mind and more slowly filtering out, and since my mind is still occupied, I'll move on reflex and perpetually forget to flip the switch.
Manual labor also require focus, but when you are occupied tends to be obvious. If you are under a car, messing around with a tool in your hand, everyone knows it is not the best time to interrupt you. In safety-critical jobs, like in the case of pilots, there are mandatory protocols that explicitly forbit interruptions during critical moments.
People usually know enough not to barge in when the manager is having an talk with his higher up or when the salesman is negotiating with a customer unless it really is urgent.
But programmers just stare at the screen all day, and most of the work happens in their head, so how do you know if they can be interrupted or not. Bad managers assume "always", because themselves only stare at the screen during their "off" time, so they assume programmers are always "off".