There are two major issues with that. First, even if the Bitcoin protocol were set as a law of nature, this doesn't by any means make it perfect per se. In fact, this whole topic is about that it is actually far from being perfect (or just good enough, lol), mildly speaking. Second, it is not set by nature, but what is made by humans can be unmade by humans too. So why should I trust it?
Why should I trust my real wealth to a relatively small group of people who control Bitcoin and who could kill it if they chose to?
I expected that you would raise this issue, lol. No, I don't. But in fact this is irrelevant, for two things. First, fiat (unlike Bitcoin) is neither meant nor actually thought as a long-term store of value. It is meant and used as a means of exchange, but being a means of exchange is antagonistic to being a store of value in the long run. Thereby it cannot be trusted by definition...
So whoever decides to store their wealth as fiat is shooting themselves in the foot... with a cannon, wtf