Don't get me wrong (I think the world of Kuerten), but Flipper tried this, too (to a lesser extent).
Something tells me he was just saying "yes, sure!" to some friends with a good idea for a business. Just trying to remain constructively involved with tennis during downtime due to injury? Maybe he was just tired of seeing the same uninspired apparel and thought he could do no worse.
Maybe he's watched one too many reruns of Queer Eye for the straight Guga.