This big wheels/big tires thing is nothing but a silly fad fostered by the manufacturers of vehicles and wheels and by kids who think big tires are macho. For example, I'm on 3 Ford Ranger forums and probably the most asked question is "what's the biggest tire I can put on my Ranger"? Its nauseating. All they care about is size, despite the fact that these large oversize tires are often detrimental in various ways, especially if certain other parts of the vehicle are not either designed or modified to accomodate the oversized tires. And then there's the significant added cost.
I don't think anything bigger than a 16" tire is necessary on any truck, van, SUV, or car. Not too long ago the 15" tire was standard on fullsized pickups and did just fine on the trucks.