People (often young people and music fans) have been using sound to claim their own public space (while alienating and exiling others from it) since the days of boom boxes, of transistor radios, and probably earlier.

But the sharp, piercing tone of tin(n)y (and somehow super-amplified) phone speakers, playing particularly grating videos or loud video calls, all at max volume, seems optimized for maximum irritation. And it's often adults, who presumably would not usually shout but are nonetheless talking very loudly into their max volume facetime calls.

I would probably find it annoying if everyone walked around listening to sports games on small radios, but it is a rare occurrence so I tend to be more surprised that sports radio (not to mention AM radio itself) still exists.

We're all literal animals.

Extremely good point! Another theory I have is that the ipad generation has grown up and they're now out unattended in public.

Your point about corded headphones being cheaper could mean that this is just a result of poorer people using public transit