We're not talking equal rights here; if a man doesn't believe that women are equal to men, why do you even want him in the first place? We're talking equality of ambition and equality of feeling.
In some relationships - maybe even relationships you've had yourself in the past - one person clearly loves the other more than they're loved in return, and the person who's loved less becomes insecure over time. If you're going to invest emotion in someone, you want to get the exact same investment back. In the same way, if one partner is driven to succeed in life and in work and the other is happy to sit back and take the easy road, that's not going to work in the long term either, because the driven one is going to feel the other is holding them back. Men want a woman who loves them as much as they love her, and someone with similar goals in life.