Why did many feminists prefer Ms as a form of address instead of Miss or Mrs?

Answer 1

It's not just a feminist thing. Many people do it for professional reasons, as not all women take their husband's name, which means she is no longer a "Miss" - which has historically referred to unmarried females - but if she's keeping her last name, she may not want to be known as "Mrs." Maidenname, which is also her mother's name.

The problem is, unlike men, the form of address used historically changed when a female was married. If you were unmarried, no matter your age, you were called Miss. So, the form of address was dependant - and this is why some people prefer "Ms." - on being married. Being addressed as "Ms." takes that out of the equation, and like men, puts the worth back on the individual and her accomplishments, and not on the status of being married.