This is a very interesting quesion since when people sell bitcoin for USD, it means they trust USD more than bitcoin

So why do people trust in fiat money, which is created out of nothing by the central banks?

Is it because they have no knowledge about money creation, or because their ignorance about the financial, or their respect/fear about the government enforcement?

One accept fiat money is because all the other merchant also accept fiat money as a payment medium, once this tradition established, it seldom changes

But this is only one reason, another reason might be that they regard fiat money as a safenet, backed by the government. Look at the FDIC rules, it just want to calm people from withdrawing their savings from banks and it worked very well

I think some kind of insurance should be built around bitcoin, to give people more confidence to handle the bitcoin. Saying this is backed by mathematics and network just scared most of them