A quick search on Google will say this below on the purchasing power of dollar over decades
Since 1972, it has fallen by 99 percent against gold and lost 90 percent of purchasing power of real goods and services.
Imagine if US Dollar were a cryptocurrency, it would have been one of the most shitcoins ever.
This is just reminder that bitcoin is a paradigm that has lead the would to a new way of doing things, and a solution to both financial crisis of 2007/2008 and Double spending. It has proven to have performed even high than Gold in recent times and is probably going to be top #1 of all cryptocurrency for as long as it keeps existing.
Bitcoin is only a decade and five years old, the interest it has yeild and it's growth over the years both in price and community support has shown its uniqueness and should be taken as a serious investment. Don't trust a currency that depreciates over the years with your investment rather take advantage of bitcoin volatility today.
Why just US dollar? All fiat based currencies are falling in value. The purchasing power is decreasing for all of them! It's not only about USD. That's the basic nature of fiat currencies. That's why people should never make bank deposit for some small percentage of return which depreciates overtime.
That's why people used to buy Gold to protect their capital in earlier times. Gold is still a favorite amongst many of us. Bitcoin is extraordinary here. It has always shown a super strong performance since inception. So it's always a good choice to invest in Bitcoin and Gold as well. It has proven itself as more than just a passing trend and should be considered as a serious investment alternative.