By it's nature, bitcoin has a limited supply capped at 21 million that will be reached in the year 2140 and as of now there are about 17 million in circulation. Due to there being a limited supply the price of bitcoin is deflationary meaning that it will increase over time. Fiat currencies have a total supply that can be manipulated very easily which causes them to be inflationary, meaning the price decreases with time. Bitcoin shares the properties that have made gold valuable over the last couple thousand years.
Although in most first world countries inflation hasn't been a problem, it doesn't mean it can't happen here. In countries like Venezuela and Argentina, hyperinflation has wrecked their economies and citizens that have even saved money their entire lives find that money nearly worthless. Just in Venezuela hyperinflation has devalued their currency by over 1 million percent.
For people around the world, bitcoin actually offers an opportunity to feed themselves and their families or preserve wealth. Even if inflation is not so apparent in western countries we should look at our current monetary policies and realize that this is not an impossible outcome here as well.