I respectfully disagree with that premise.

Of course it's best to save more, but that's not always plausible - for example, when I completed my PhD I was earning $31k/year for five years, which was not very much with a wife who wasn't allowed to work and two young children. At that time, saving even 10% wasn't plausible.

As for working longer, sure, you can do that if you choose, assuming your health and the job market allow it. More than 1 in 3 Americans who want to continue working into their 60s find that they cannot, whether due to health issues or getting laid off and not finding new work.

In short, investing solely in TIPS or I-bonds is not risk-free. You're simply changing the risks you take from market risk to health and job-market risks. The former is something you can adjust for ongoingly as your portfolio grows or shrinks. The latter you find out only when it's too late to do anything about it.