I think you're ignoring the point that if you want high-quality gear, it's cheaper to buy it outright and store it off-season.

And the kinds of people who live in places where they don't have room to store a surfboard year-round, are the kinds of people who don't have a bunch of wall space for one either.

I think you might not be totally understanding the concept of small urban apartments. Putting skis in the closet or under the bed year-round doesn't work, because your closet and underneath the bed are already full. (And it's not just skis, obviously -- it's boots and poles and helmet and bulky jacket and snowpants and gloves and everything.)