The main point of btc purchase is to earn more fiat in the future. Thats how and why the majority of people invest in crypto
You didn't answer the question that the thread asks, I know that it is not possible but we have to assume that this thing will happen to bitcoin in the spirit of being on topic in this thread. I think that purchasing power is a narrow mindset if you want to use bitcoin, there are other ways to get a purchasing power but what makes bitcoin different is that you are responsible for the loss and gain of your money, if you lost it then you have no one to blame. I guess that you are right about the money making potential of bitcoin that makes people interested. If the prices were to plateau and never to go up or down again, then I will take the chance to buy myself a good portion of it and hodl it and sell it OTC where I can sell it at a higher price although it will be difficult at first because there are a lot in supply.
It definitely won't make a good investment but it will get its value increased on the streets
@Lorence.xD is onto something here but I disagree that when that thing happens it will still be a good investment.