Most modern cars are aesthetically designed to feature large wheels. Vehicle designers claim they improve the overall stance of the vehicle. Large wheels also improve road handling and grip, due to the fact you increase the contact area of the tyre with the road.

But, as you rightly point out, large wheels and low-profile tyres will make the ride quality hard and bumpy on less-than-perfect road surfaces. However, with large wheels being more popular than ever before, it would appear this is a sacrifice that many drivers are willing to make in order to have a car they deem to be aesthetically pleasing to the eye.