I would challenge you to look at your question but expand that to any currency. Is the USD or Euro backed by anything? The answer is no. It is ultimately the faith in the currency that gives it value. What is interesting is the same is true for commodities.
Did you ever wonder why shows that show royalty 300+ years ago have them eating out off aluminium plates? There was a time when that was a metal more valuable than gold. Interesting how things changed.
How much do you think oil will be worth in 40 years when most, if not all transportation is non-gas powered? I am going to guess it wont have much value.
So ultimately, the question is why is anything worth what it is? Where does the value come from?
@taskmaster4450 Thanks for your thoughts. In fact I mean a more narrow question than the asset backing. Some coins are experimenting with an commodity price relationship. I'm considering that may compromise any decentralization to the coin. It can still work as a cryptocurrency of course. The blockchain is versatile.