The reason bitcoin core has not changed is because it cannot get 95% consensus to change. I like that. Unless virtually everyone agrees it will stay the same.
Bitcoin Cash and the others are all running on the claim of speed and lower fees because they are 2X or 8X or my grandmothersX. If Core was sure there were no security risks injected with this $100B+ baby they could change a line of code and make it 16X. So I ask, if they do make it say 8X, does the value of bitcoin cash all of a sudden disappear? You would have all the advantages of bitcoin cash plus all the enhancements that came with segwit. Your centralized BCH would instantly be under SERIOUS financial competition.
If I am an institutional investor, I will leave my money in bitcoin where it is decentralized and not in BCH where they make code changes anytime they want like changing difficulty, or later the number of coins, or charge a 20% tax for personal use, or whatever they want to code.