Political will for transferring wealth from certain portions of the population to others can change quickly. Also, the pension amount likely will not keep up with real inflation, as is the case today.

People can just have higher salaries and save for themselves for their pension, just like any other expense they have in life.

There is no practical need for this to be centrally managed, other than you can't trust people to be responsible and plan for the future.

People already manage a big part of the pension savings by themselves.