Yeh the FX currency markets are far higher on capitalization than cryptos, in fact currently cryptos are far bellow equities market cap.
But really all it matters is to think 3 steps ahead merging the use and view on market to see where the market cap of cryptos will move.
Think of it this way the blockchain projects are able to deliver useful projects that actually absorb and create value which replicates the companies and stock markets.
On other hand you also get the function of currency which not just replicates the features of fiat currencies like EUR or USD, but it actually creates far more powerful improvements in terms of speed of transactions (very important), deflationary market, young market with growth potential, etc etc.

So what you get is merging of both equity and FX markets features, which opens massive gates in future for capital inflow into crypto markets. Blockchain gives you ability to build on top of it pretty much any system.
Now think of it that way, internet and the softwares, companies, products that are build around it together have value of trillions of USD of market cap. But the thing is since internet does not by default use its own monetary system its market cap is splatted all across, some in equities (internet companies), some in FX (transacted value of fiat currencies that internet bussines use) which then leads to market capitalization that is spread all across. Crypto market cap is however bound together, which allows for far higher % gains if one is investing in since first of all capital has to go trough main gates eg BTC and then sit in ETC or ETH and its derivates as secondary option. This means if one is invested in either of those 3 main gates potential for future profits from increased market cap is huge.