Because if they accept fiat(paper money), meaning, they need to have a special licence & approved by the government for each of every country that is using their platform to deposit fiat.
So this is why most crypto exchange only accept BTC (or any other crypto currencies). So they no need to deal with the licence on each of every country.
Because all of this problem already been solve by coinbase, luno, etc.
This is how BTC become king of crypto.
Now I wonder how OXY gonna achieve this? Buy "any" crypto with fiat. If OXY really can achieve this, OXY gonna be huge.
https://coinmarketcap.com/currencies/oxycoin/
