Why north Indians migrating so much to MH and south indian states ?

I was looking at stats , literally 27 lakhs UTTARPRADESH people migrated to MAHARASHTRA alone for jobs . 1Cr+ bihari people migrated to MH, GUJRAT and SOUTH INDIAN STATES . This migration is increasing day by day . I feel very bad for them coz some of them living in very worst conditions but some of them creating problems in this states , they don't learn local language , don't respect local culture , lack of civic sense . Due to this anti immigration sentiment increasing in this states . Literally 80% prime ministers were from UTTARPRADESH constituencies . Despite being epicenter of national politics why north india especially UP ,BIHAR ,MP people migrating other states for jobs ?