Bonds don’t pay out much over inflation, and most retirement plans bank on contributions making much more than inflation to be solvent. A lot of our debt is simply savings for retirement on the other side, it is very necessary for anyone to invest these days (directly or not) if they have any hope of not being destitute when they can’t work anymore. More than that, even if we left it to the government (eg a better funded Social Security), they would have to invest as well, there simply is no way around it given current moribund population growth.