You could say the same thing about social security too though I don't think I'll get back >= 100% of what I put in. Between "means testing" (which is stupid because it disincentives saving) and raising the retirement age for non-boomers, it's not looking probable so don't consider your 401k untouchable either.
When I started paying into social security they promised me retirement at 65. If an insurance company changed the terms of my payout after collecting years of premiums, they'd have a fun lawsuit to defend.
For the most part, they are backstopped by state-mandated-private guarantors (who in principle also have a bankruptcy risk), but not federal guarantees, and with fairly low limits (and sometimes at less than full value even before the limit, e.g., life insurance products on CA are at 80% up to either a $100K, $250K, or $300K limit, depending on the type of product.)
The easier way to move money from savers to debtors is to cause inflation, but good luck getting that to happen in today's environment.