BTC is gradually gaining its grounds in the financial institute. Most people prefer using bitcoin as a medium of exchange. Before the advent of bitcoin local and foreign currencies were the only means of financial transactions. Currently BTC has gone beyond bothers and has also made transactions safer and faster without much stress of converting from one currency to another. From my own opinion its a better way of accumulating wealth and secure a perfect future of cashless policy
It's not that they prefer it, but it is because it IS a medium of exchange, plus, most actually consider it as an investment even instead of a currency. And afaik, Bitcoins speed is still an issue, and that's why the lightning network is being introduced right now, though it's still at its infancy stages. Plus, if that were all Bitcoin could offer against centralized fiat, then the Government and banks could simply create their own digital fiat, with their own centralized system to make it faster. Such developments have been oddly delayed for some reason, but it would naturally be made in the near future.