Why has no one tried it?
1. Technology is barely at the point where discussions become meaningful.
2. Funding is unavailable. Lenders won't touch it. Lenders need some proof of ownership, and you can't claim a celestial body and so have no ownership.
Transorbital seems to be finding funding. There are other ways of raising money than loans. It is not necessary to claim a celestial body to mine it. There is nothing in the Outer Space Treaty that prevents private mining of bodies, or ownership of the proceeds, no matter how many times you repeat this canard. Possession is more than nine tenths of the law in this case.