They do it for shock value and under the illusion that it is somehow "keeping it real." Fear not, we are not turning into a nation of Eliza Doolittles...though, wouldn't it be love-er-ly?
Unfortunately, a large segment of Americans use far less of the available words on English,because they don't know them. English is a wonderful language,most of which has gone into decline from disuse.It did NOT used to be this way...even poor people knew more English than most in the middle class know today.*sigh*