Headphone Mode = Do Not Disturb

Sorry, I cannot agree with this sentiment.

You are paid as a servant of the company and that duty includes responding to and assisting your co-workers.

Perhaps they are interrupting you because their work is more important than yours, perhaps not. But that's not your call. Raise it with your manager, don't resort to being ignorant.

If your environment is not conducive to achieving assigned tasks then raise that too with your manager, don't resort to being ignorant.

I have several friend who are commercial pilots, they wear headphones all the time when on duty. But they will absolutely give attention to anything their cabin crew asks them, no matter how trivial, because the team is what ensures a safe flight.

Some of the people on my team have headphones in all day every day... that makes all the time Do Not Disturb.

This post shows that you don't trust your team to communicate. If someone is interrupting so often it is disrupted it is up to the team to communicate that. And if need be, have a manager mediate.

You should also be able to tell someone who interrupts you at an inopportune time that now is not a good time and ask them if they can wait.

On the flip side, the rest of the teem should know that other people's time and concentration is important / expensive and be respectful not to interrupt when not necessary.

Programming especially is a team sport. Doing this is not being a team player.

I'm all for social cues to tell others now would not be a good time to disturb you. I just think this kind of absolute is not the right way to do it.

With that said, if it works for this particular team. More power to them.

Edits:

Also, I have headphones in all the time because I like to listen to music. But I don't mind be interrupted (I'm a manager, it's my job to keep people moving and if they are stuck I want to know). So am I only allowed to listen to music when I'm in DnD mode?