Massive difference in education/qualification between average police and nurses. You need a high school certificate to become a cop and at minimum a diploma for enrolled nurse or an undergraduate degree to start on a career as an RN and with specialization the skies the limit. All that time and expense studying while a police officer can be earning good money.

Pay for nurses and to some extent teachers has a basis in historical sexism. Even as these occupations became increasingly professional and demanded much higher levels of education they retained the stigma of being womens jobs. Its a joke.