Most people I know that have done it have done it for the attention. Once that wears off they are back to eating meat.
adopting a vegetarian lifestyle takes time, research, patience, trial and error and most importantly, money. When young people realize how bad the OTC stuff tastes and how difficult it is to make the vegetarian options mimic the taste of meat, fish etc, they slowly return to reality.
I've heard it was like that in some parts of the country, but here in the Northeast, nobody gives a rat's ass if you're a vegetarian. Plus, people who keep kosher will often eat vegetarian in restaurants.
My two daughters and my niece all went through a vegetarian phase beginning in high school that lasted through their early 20's. Never strict vegetarians, just for a time disgusted by the thought of eating flesh. They all still ate chicken stock, etc. Of the three, only my niece is still a vegetarian. But neither daughter eats much beef - pretty much they stick with chicken.
My wife thinks ham too closely resembles human flesh and still won't eat it, though she cooks it for us on Christmas and Easter. I love ham, but that much sodium raises my blood pressure, but I figure twice a year won't kill me.