Have you actually looked at the CISSP material recently?

It's a hodge-podge of everything under the sun. The only thing it's able to prove is that

a) you have endurance and spare time to sit for a 4-6 hour multiple choice test

b) you can commit to rote memory a bunch of meaningless material which you are unlikely to encounter in real security/risk management role

It truly is the worst of the bunch, but for reasons yet explained, it's the defacto "must have" by bigCorps - which is why it gets picked on by so many folks: everyone knows it's bad, yet most people end up picking it up.