Answer: Legal ambiguity carries its own risk.

Therefore, rates in more ambiguous instruments should be higher than those in more certain ones, no?

The risk-free rate in this sector is substantially higher than 4%.

If the value of crypto is that it drives down the risk of lending by bringing transparency to the assets of borrowers, then how can the interest rate be higher than in the normal financial system? The fact that there is less risk but interest rates are higher should tell you everything you need to know about why this is a scam.

The question is "Why is there often 20% per year or higher cash-and-carry arbitrage for assets that have near zero carrying cost?" The answer might be that every crypto exchange has a 15% or higher chance of exploding per year and they've all just been extremely lucky, but I wonder if this is really the best explanation we can come up with.

It’s not risk free, US Treasuries are ‘risk-free’ and anything that pays a higher yield has risk. If it didn’t have risk, it would be arbitraged down to the risk-free rate.

And even the risk-free rate on[1] Treasurys is being held down by tremendous Federal Reserve purchases. (The Fed doesn't buy crypto loans, or at least, won't until Goldman Sachs keeps some on their balance sheet.)

[1] at least short-term

You can post that markets are efficient and I'll keep making money from obvious inefficiencies I guess.