Risk is the chance something bad happens to you.
Held for 30 years, bonds are eaten alive by inflation. That's a bad thing that happens to you if you hold bonds for a long time.
20-year and 30-year bonds yield 5% today. That's well above inflation expectations.
You can actually buy inflation-linked bonds that are going to pay you 2.5% over inflation for the next 20 or 30 years - whatever happens with inflation.
I'd argue a much better 30-year bet is that somebody like Coca Cola will be able to charge an amount for their product that reflects whatever happens with inflation much better than betting on a fixed rate of 5% that can never increase.
I didn’t say anything about “risk-free” (the closest is the second paragraph but you don’t address it at all).
I was clearly commenting on the quoted sentence “Held for 30 years, bonds are eaten alive by inflation” which has not applied since the seventies, doesn’t seem the best assumption going forward, and has an easy solution as discussed.
> reflects whatever happens with inflation much better than betting on a fixed rate of 5% that can never increase.
If your main objective is to beat inflation, getting inflation + 2.50% with certainty seems an attractive proposition! (Inflation-linked bonds have a “fixed” rate on top on inflation.)
Given the ever increasing number of people bankrupted by medical bills, divorce, child support, lawsuits, etc we're quickly moving into a world where it might be foolish to expect assets accessible to a brokerage or bank will still be there by the time you need them.