I look at that in different way - my gain doesn't exist till I have Fiat from it.

Your statement is like because you have used bike instead of taxi or rented jet.
You saved that way lets say 20$/1000$ you should pay tax from that income.

So as you say:

"For example if you trade bike ride for jet fly, you must pay taxes on any gains you made from that trade."

My IRS wanted tax companies using Linux they wanted VAT equal of Microsoft Windows because they were not using Windows and got gains.
Some tax offices are just more than ridiculous and you spend years in court to prove your rights.

You can pay tax from trades ETH/BTC but I will never do that until I convert that crypto for Fiat,
because my gains have to be proven by market.