It’s certainly not for their attractive interest rates and repayment terms! People are mainly tempted to go to loan sharks because of the lack of red tape, which may be problematic if they approach conventional lending institutions, and the fact they can borrow what they like.
Loan sharks are not interested in credit scores, employment records, or pay slips. People who don’t have regular, sustainable income they can evidence will be turned down by standard lenders, or it can take too long to process the loan.