Why do people make fun of bihari people doing manual labor jobs ?

This thing is really beyond my comprehension where people make memes where they use the word "bihari majdur" to insult the people of bihar like whyyy??? They are doing jobs which is a must to do job for the country and for they people , they are not doing anything illegal . They are doing one of the most important jobs of India or the world . Where as they themselves are going in other countries " ILLEGALLY" exploiting the system and job market and are well known for their bad behaviour in countries like canada , overall bringing shame on the name of the country and community . I know bihar have problems and people lack some civic sense so does all India , its about education socio economic status where bihar performed poorly due to politics so it comes out loud .