While I'm not the most careful person in the world, I'm also not the most incautious; I think it's probably not an uncommon experience for people who do regularly ride trains--e.g. those of us living in big cities where you commute by train instead of your car--that you sit and you realize you're sitting on your coat in an odd way that's got your phone in the pocket underneath you where you're sitting.
I mean, at some level, come on and use your imagination. People riding the metro don't always have total control over getting their belongings situated properly when the train's packed and there's a lot of bustling around. I assure you this experience is not unique to me.
That's weird, it took me half a year (commuting daily) to go from "carrying phone in jeans' back pocket is practical" to "I have to take out phone from the pocket _every time_ before I sit". No problems ever since. But I guess I learn fast ... Unless it's setting up some wireless crap.
Hey that's great. You know what? With the wireless earbuds, I never have to think about that again. I can throw my phone in my pocket, any pocket, and leave it there while I get crammed into a metro car.
So, I guess there are tradeoffs -- and fixing pairing means everyone can enjoy freedom from one more wire, while keeping on using a wire means we keep adapting our behaviors around a wire.
Don't forget that you can still have a headphone jack AND bluetooth, the problem here is the removal of one as i'm sure many people would be mad if nex gen phones would dump bluetooth and use wired-only audio.