It’s the fear or apathy of the asshole to retaliate. I could be on a bus, and there could be an asshole playing music without headphones. Saying something could come with verbal abuse at the least and could end in a physical altercation with or without weapons at worst. As the annoyed passerby, is confronting the asshole worth the effort and risk for quiet?

I love calling people out when I can, but you gotta pick your battles.