OK, a torque wrench has a long handle because the length gives you leverage to apply more pressure. The longer the handle is, the less you have to push to break the nut loose right?
It is the same thing here. When you add those 20-25mm spacers, even the Ichiba V2s, you are making the 'handle' of the wheel longer. This means that your normal 3200lbs car is now exerting more force on the wheel studs than they were designed for, and they can shear off.
You can get away with this to some extent by using wider wheels because when properly fit, the offset is calculated to not add additional strain as you are adding width towards the outer fender and towards the inner fender wall. If you were to get a wheel that is 20mm wider, it would be 10mm closer to the inner wall of the wheel well, and 10 mm closer to the outside of the fender.
You would not want to get a set of wheels with a crazy offset that made them stick way out, it would be the same effect as big spacers. In fact you would be hard pressed to find a shop that would sell or mount wheels that are like that as they are dangerous. The only way you could get buy with something like that would be to replace all your wheel studs with ones that are way stronger, then shortly after when you realize the geometry has killed your suspension, be prepared to pay big bucks to replace everything at all 4 corners.