Is your boss over 45? It could just be a generational thing. For context, in my younger days, I worked in offices where no one ever (literally NEVER) took a personal phone call unless it was an emergency (this is before mobile phones and texting). And it still looks strange to me when I see people working at an office with headphones. (Even though I prefer to work with music).
What does 45 have to do with it? I'll be 60 this year and I often use headphones in the office, my boss doesn't care as long as I don't drum too loudly on the desk while listening to Deep Purple, Led Zep, King Crimson, Scooter, etc., etc.
I mean really, people my age and older invented the personal music player and so on. You could make a good case for saying that Masaru Ibuka invented the Walkman at Sony and he was born in 1908, around about the same time as my grandfather! He was already 70 when it was launched.