Not all that many use it as a currency, hardly anyone really due to high cost and being slow.
Beyond that, it does not work well in the current form as an instantaneous payment methodf that some people want it to be.
Always the same pattern when the discussion moves to bitcoin as a currency. People who I bet have never actually even tried to used bitcoin as a currency come out and declare that bitcoin doesn't work as a currency and no one uses it as a currency. Meanwhile, there are people like me, who use bitcoin as a currency almost every day at a variety of different merchants. And all these merchants I spend bitcoin with certainly aren't accepting bitcoin because 1 customer (me) spends it there.
Bitcoin works great as a currency. Its fees are lower than that of credit cards, Paypal, etc., it is faster to confirm than every form of fiat transfer except handing over cash, there is no risk to the merchant of receive counterfeit cash or chargebacks, I can pay anyone in the world with no conversion fee, transfer fee, bank fee, exchange fee, etc. There are plenty of people who spend bitcoin as a currency and plenty of merchants who accept it. Claims that "it doesn't work" or "not that many people use it" are provably false.