If their music is too loud to hear the fire alarm or other alarms. There were places that I worked that hearing an alarm would save your life. When I was a supervisor I should have said no ear buds, but that’s a bit ridiculous. So I only got on a person’s case if they had both in, a compromise. This way the teen sweeping can listen to their music and hear a hazard alarm if it happens. Workplace safety is important.
It’s a respectful xenophobia though. Like, it’s just as bad but entirely Japanese in flavor. If I had to make a ham fisted metaphor.