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.