The dollar today is devalued and worth so much less these days - government controls the money supply and keeps issuing more money 'quantitive easing' which causes 'inflation' and so FIAT becomes worth less and you can buy less with it. Also watch out for greedy corporations that reduce the portion size of everything so you get less food in a packet  etc etc.

Bitcoin and cryptocurrencies are generally deflationary and have the opposite effect on your funds - their increasing scarcity is designed to work the opposite to FIAT. That is why I am a big supporter for our ecosystem.