The fixed currency supply guarantees it: unless the economy is shrinking at the same rate, each BTC becomes more valuable over time and that’d cause purchase prices for goods to trend lower.

This has been a key part of the sales pitch for a decade: buy now and it’ll be worth more later, guaranteed, but that’s not good for an economy since it heavily incentivizes holding onto anything you aren’t forced to spend. Since Bitcoin has no innate demand, that’s an especially dangerous cycle since almost everyone has alternatives.