Because people are judgemental by nature
Ghetto I think is a condition imposed on those considered inferior by a judgmental majority to keep them under control.
Redneck comes from the coal mining disputes with union workers and the owners of companies.The union workers needed to distinguish themselves from the company goons so they wouldn't shoot each other by mistake. They wore red handkerchiefs around thier necks. Hence the term Redneck
They're not called "ghetto". Excuse me, but, the big bad "N word" is what is typically applied. Whites are refered to as "white trash". The poor never get a break.
you couldn't call poor blacks red necks they have too much class so they had to invent a term black people bathe and brush their teeth and don't smell like cigarettes and *** till they hit the absolute gutter.