The value in your job isn't your output, it's the organisational outcomes that occur as a result of you doing what ya do.
Some companies are fine and built around the outcomes of 5 hours a day of your code. Some organisations though really want 8 hours a day of access to those sweet, sweet neurons. Even if the constant interruptions, meetings and feelings of unproductivity are side effects, perhaps they value the outcomes of 2 hours a day of your code and the value sharing that comes from an inane question at 17:59, more than absolute output.
Not saying the latter is more efficient or should be right, but just showing there's different value companies derive from their employees over and above project deliverables.