That's why you should prepare the inflation.

iPhone prices in BTC have decreased for the last decade, which means BTC value has increased during that period.

Inflation is mainly caused by money printing. Central banks such as FRB print tons of money to expand the scale of economy for their countries. Increased money supply can affect to increase new industries and companies, as well as the productivity. If money is not circulating, growth of economy will be impossible. That's why central banks set the inflation in 2.0% and printing money. They want to make money devalue to circulate in markets and corporations.

Good assets such as S&P 500 and BTC have been good options against the inflation. Wages have not been much growing compared to good assets. If you don't invest anything and save money in banks, it would be risky. Not having risks, it's rather risky.