In reality it is completely the opposite. Car manufacturers go to massive lengths testing their cars to make sure that they have the best compromise of characteristics, especially to make it consistent and safe for drivers with ordinary skills under a massive variety of conditions. On a race track, the aim is the best lap time. The driver has to cope with the other compromises and has much more skill to do so. A race track is also a much more controlled environment. You know every dip and odd camber, you know the surface coming into a corner, and you can adjust a whole host of settings on the car for each track.

For the layman to make fundamental changes to a car could be viewed as irresponsible. Most of the time we get away with it as we drive way below the capabilities of the car. However, under the wrong conditions, you may find yourself in a ditch when if you were in an unaltered car you would have coped. So you make changes at your own risk and knowing the risk is a good starting point. With all due respect, not being able to feel that the car handles differently with such a major change as far as a road car is concerned is no proof that it does not handle differently.

I'm also not convinced that sticking out wheels looks better than where they were originally put on these cars with already huge wheels and tyres. When I look at mine, any bigger and wider would simply clash with the flow of the car. Might work on a boxy BMW but on cars that are elegant and well proportioned to start with, it just looks like one is trying too hard to make it look like a track car.

 

Each to their own!

 

Even if the components can handle it, the car manufacturer needs to be conservative in wheel placement to avoid tire rubbing at the suspension upper limit of travel.
If you push the wheels outward, and have a beefy tire, you could have some (or a lot of) fender/liner rubbing if you ‘bottom out’ on a large bump.
They don’t want to get complaints about it.
You, on the other hand may decide to take that risk. Your car, your choice.