The 4% rule means we all have to individually save enough to be 90% confident of having enough even in case we live too long and even in case we retire during the worst market conditions. If everyone retiring has to plan for that level of confidence, then 90% of us will die with way too much money. We will have way,way underspent. By pooling all our savings we no longer have to individually bear this burden. If some guy in the pool gets hit by a bus the day he retires, we get his money. Everyone saves a lot less, spends a lot more, and the insurance company manages it all for a cut. Social Secutiry works this way, sort of. So do most forms of insurance. By sharing the risk, we all benefit.
Just make sure the insurer doesn't take too much and that they stay in business at least until you die.