Since the mid 2000s they started using Gas Direct Injection which puts the fuel injectors inside the combustion chamber. This now means that the fuel does not mix with the air before the cylinder head and thus the fuel/air mixture (nor fuel injector cleaner) will not do anything to help keep the intake valves clean from carbon buildup.
This problem is compounded by the pcv valve system in turbocharged/supercharged cars. The pressurized air from our turbos finds micro holes to leak out of and ultimately pressurize parts of the engine that are not supposed to be. Thus the PCV system allows that air to recirculate to prevent catastrophic engine damage. The problem is, that air is now filled with oil and other contaminants that then coats the intake valves.
An oil catch can is added inline to that pcv system to catch those fluids. Now, there is many who avidly argue for them, and many who say they do nothing, and there is no real conclusive proof of 2 cars in the exact same driving environment for 60k miles to say one or the other.
IMO it is logical that it would help reduce carbon build up, but even if it doesn't, I am at least catching that contaminated oil from getting into places where it is not supposed to be, and it is only $200 and very easy to install.