I don't really see it as a stark contrast. Pensions and social security may be accounts where money is coming from someone else in the future. But a 401k is only semantically different. You do not own your 401k account in a real sense. That money is locked and kept away from you. You can only withdraw that money according to the rules in place at the time of the withdrawal. If you wanted to take that money out now, you would be paying the penalties in place that exist today. In 20+ years from now, when you intend to withdraw, you will be doing so with the laws in place at that time. And what those laws will be are unknown at the time. The same as current conditions were unknown to partakers in pension funds and social security a generation, or two, ago.