It’s simply the fact that visual beauty is easier to detect than the other forms. It is the most apparent, it is the one that screams out at you at first and can often be so beautiful that the other ones are not even detected. Visual beauty you can detect right away. Inner beauty is something you are going to have to work at to get to. You can’t just get it right away. As far as I’m concerned, a relationship will not work if the inner beauty isn’t strong enough. That said, I don’t think visual beauty is inferior to the other forms just because it is often more obvious. Paintings, photos, and landscapes are beautiful and just because you can see that right away doesn’t mean it is somehow less powerful. Additionally, visual beauty can be quite deep and goes beyond what is seen on the surface. People might not see past the surface right away, that is asking a lot of the mind. It takes a little time to see past the surface and discover what lies beyond the surface. Once they discover how beautiful that truly is, then it may end up being much more important than what is on the surface.