This is the fundamental thing that I struggle to grasp. It is said that Bitcoin is a store of value which can preserve your buying power over time in relation to fiat currencies.

However, it seems to be frowned upon to consider the exchange rate of BTC and fiat currencies. How can this be until BTC is a unit of account where anything can be expressed and purchased in sats, wherein I can go to the grocery store and see a gallon of milk expressed in sats and not fiat?