RELATIONSHIP BASHING

. WHY DO PEOPLE TRY TO BASH THE PERSON U ARE DATING?? FOR EXAMPLE, " EWE GIRL YOUR MAN NOT ALL THAT, I THINK U COULD HAVE DONE BETTER OR FOUND SOMEONE FINER?? OR A GIRL TELLING A GUY, " YOUR OLE LADY ALRIGHT BUT SHE NOT ALL THAT, U COULD HAVE FOUND SOMEONE BETTER OR PRETTIER ?? MY QUESTION IS WHY DO PEOPLE DO THIS???