It's no different than someone who expects their partner to handle the majority of housework and childcare when they're splitting expenses evenly. In both cases you're expecting something without giving anything in return. You're being subsidized because you both use the home and utilities equally yet you're paying less than them.

This talking point is frequently used by women to paint a seemingly gender-neutral veneer over their entitlement to male provision, when in reality, the vast majority of women seek men that outearn them and few would be willing to seriously date men that earn substantially less.

If the higher-earning partner(overwhelmingly male) is living within your means, splitting expenses equally is the fairest arrangement. If you were living with a roommate you would, in all likelihood, split rent and utilities equally, or at most with a small disparity based on room sizes and bathroom access, regardless of how much either you earn. Why would it be fair to demand more from a partner?