Well I'm far from an expert on this, but my understanding is they are made to be extremely light, for race purposes. This is good when you're only going to do maybe 1000 miles (thats a lot of quarter mile passes!), but for more heavy duty (daily) driving, a wheel needs much more material on there for support. A lighter, weaker wheel just doesnt hold up.
EDIT: Re-reading your post, I realise now that I misread it. I saw "weld" and "wheels" in the URL and assumed it was linking to Weld Wheels:
http://www.weldracing.com/ which are custom made lightweight spools for race-only applications. The link you posted is completely different... honstly I'm not sure how those would hold up... Weird...