This is a species of sub-human called an "asshole", defined by a total lack of the social skill known as "The Golden Rule". Then do what they want when they want, without a bit of consideration for its effects on other people.

You can find them just about anywhere, but situations like on the road where they intrude into your activity, or being trapped like you were on a train, are typically where their attitude of "no one else is real and has wants and needs, except for me" truly shines.

Cell phones are merely the latest way for the Asshole to make his presence known, it's direct predecessor was the boombox used to share their shitty taste in music with the known universe. It's current iteration is the car with the absurdly high-powered audio system and windows down blaring their shitty music.