No graphical techniques shoudl ever be mandatory, it's far better that it's left to the artisist and technical team to asses the best use of resources.
Also, it's worth pointing out that no game does global illumination accurately, there are always shortcuts that have to be taken to get the games to run on the available hardware. That's even true with high end offline rendering. For global illumination to be done accurately it would need an almost infinite number of rays and it would also need to calulate how much energy is used by each photon each time it comes into contact with something, how much energy is left in the photon once it leaves the object, was other objects does the photon come into contact with after it's left the first object, how much is absorbed by the second point of contact and how much is bounced off again, etc. etc.
Even with that, it's really oversimplifiying what would need to be done achieve it accurately.
"Faking it" has always been a large part of computer rendering and it likely aalways will be.