As an investor in the stock market I am forced to do this using fiat currencies. I would LOVE to do this using cryptocurrencies and bypassing any broker. One of the biggest fears I have as in investor is that if a real market crash occurs, economies world wide crash and banks need to be bailed in, they will confiscate everyone's profits. If people could just make trades in cryptocurrencies and immediately send their profits to their wallets after selling their assets, governments can't confiscate the money you earned by being a smart investor and brave enough to take risks.
This is just an idea that I am having. If anyone thinks this is feasible, please let me now.