For the record, I have nothing against SC/FCY as a
feature, one my personal pet favourite would be the ability to yeet around in an SC like Maylander.
The two key decisive factors are:
Complexity, integration and making sure all bases are covered and you don't end up with something that takes away from the driving/racing experience if you can't feasibly do that, i.e. leaving open outrageous exploits or not finding a threshold that keeps it a cool novelty rather than a frustrating chore.
Gameplay value, as I mentioned earlier, there is the competitive aspect, where it really only exists in real life as a safety necessity with ugly side effects, and more often than not it has a detrimental effect on the outcome of the race, but even if we discard that, there are things higher on the imaginary list that also didn't make the cut - more destructive damage, terminal damage without ability to RTG, debris scattered around, track damage - the lack of which make it rather pointless and arbitrary for no real immersive value and without obvious justification from the virtual environment.
I understand that we could just do all that and that would be cool, but there's always price to pay somewhere else, and prioritizing other things have allowed more immersion elsewhere that arguably maybe hold more actual value. Also, devs are a limited species and the ones that may be tasked with tyre models and physics fidelity know jackshit about gameplay code and vice versa, so saying that we could do this or that instead of adding cars/updating tyres/adding graphical features doesn't really hold up. I've been personally offered €1,000 by a user if "I fixed VR", but unfortunately that's not how it works.
The reality of game development is that if there's enough complaints or feedback supporting the need for a feature, it usually gets added eventually or in the next project a studio might get involved with, but resources are finite so that would always happen to the detriment of something else, and in the end you can evaluate which group's complaints were worthy for the exchange.
One day you might get your SC but it won't be without casualties, and this is what developers juggle with on a daily basis, and then you still get told off when some other thing from 1993 that is supposed to be on Moses' stone tablet of simracing standards gets omitted for one reason or another.