The main benefit of bitcoin being decentralized is that there is no entity in the world that controls it, while banks and fiat are centralized where the ones who control it can chest the system.. No one can just make bitcoin out of nothing without mining it while fiat can be inflated by printing out more money that adds to supply. Somehow bitcoins value that it has now is it's real value and reflects the real demand for it because no one controls it. On the other hand fiat's value is just determined by higher ups.