There's a kind of fresh air that gives to a relationship -- the unspoken undercurrent is "I could leave but I don't want to" vs. "it would be incredibly difficult for me to leave, so I really hope things keep going well". The dependent spouse has far more skin in the game, in every interaction, whether the earner takes advantage of that or not.

If you're both comfortable that you're capable of making a good income at short notice, that would have a similar effect (and one of you can take some time off when you have a kid, travel the world, etc.), but you'll need a solid career first to give you that confidence.