You can not buy Bitcoin, or you can not buy anything else, but you should remember that cash is also an asset. In essence, you use cash to account for the proportion of wealth in the whole society to participate in the distribution of social resources, which is the same as taking any other assets to participate in the distribution. What's the difference? Some assets will gather more and more consensus, so other people's wealth will run to your side; while some assets will lose consensus, then your wealth will run to others.