The issue is a few fold. First, you want to get the right width of wheel for your tastes and driving style. Next, you need to find the right offset in order to get that style of wheel positioned right under the car. You will have steering and suspension issues arise if your wheels are too far out/too far under the car. Then you have to figure out if the clearance inside will allow for the calipers to clear. This usually isn't a problem of space radially, rather distance from the face of the caliper to the inside of the wheel spokes.
The problem is people seem to think that offset is the only issue. If you go and throw a wheel on with an offset that puts the wheels too far out so that it can clear the caliper, you have those steering/suspension issues. They talk about that over at SPD USA.
I'm not 100% sure that you won't be able to use ANY wheel with a lip, but it just seems to make sense that if we are concerned about having enough space for the huge calipers, you wouldn't have the luxury of having extra wheel/tire hanging to the outside without looking like a roller skate.