Each asset holds a value, often priced in U.S. dollars, which leads to another use case: trading and investing. Aside from stablecoins — which seek to stabilize the instability of cryptocurrencies by pegging an asset to something else, such as the U.S. dollar — most cryptocurrencies constantly fluctuate in price. You can trade between cryptocurrencies and national currencies (called fiat currencies) on exchanges, depending on the trading pairs available on the platform of choice.
Mr Rocket also cited some concerns over whether there is a "strong liquidity pool" or not.

But this time feels different. It feels like a bubble. The fever in the post-Thanksgiving moonshot ran hotter than we’d seen before. We also began to see a robust supply response.
Overall, it appears from these results that cryptocurrencies may experience short term intervals of co-movement, caused by sector wide news or cross market contagion, though correlation is likely to change dependent on the nature of the causal event and market environment. In the medium and longer term Bitcoin and Litecoin are strongly related; it is believed this is due to their similarity.