It's not. What you say is true, but there's a crucial difference. 65 million people live in the UK and all of those have to pay their taxes in GBP. Also, all listed companies in the UK are listed in GBP. That guarantees that there will always be significant demand for GBP. Not the case for BTC. Note that I'm not saying that there WONT be other reasons that could generate demand for BTC, I'm just saying that BTC is nothing like GBP.