So we should use blockchain to control gold and silver market maybe not whole market but certificate part.
Using the blockchain will allow to control individual bars deposited in any treasury and prevent you from "selling" the certificates of the same bars to several people at the same time..
Yes, we should/could/would do just that.
But Wall Street is not likely to do that. They are likely to sell you something like a mutual fund. And they will claim for example that x% of it is in Bitcoin, and an other x% of it is in Litecoin, and so on....
Your mutual fund investor is not going to tell you to go buy coin to keep in your wallet because that would directly remove him as the middle man.
When others rejoice in Wall Street getting into cryptos, I don't rejoice, I cringe.
I think you fail to understand how much money is being made from rehypotecation and fractional reserve banking. Bankers are not going to give up that cash cow any time soon.