I see alt-coins could be seen as derivatives, but I think they have several other functions, I use altcoins for purchasing products, holding savings, and keeping one out of corrupt banking and taxing systems, altcoins like bitcoin was made to resit inflation because of their decentralization system of operation.
derivative examples I know... futures, options, swaps, synthetic collateralized debt obligations and credit default swaps.
And since so many cryptos are token 'izing real world assets they are becoming derivatives in their nature too. And i genuinely hope that you are right about the reason why BTC and altcoins were created, as i have other suspition, but that might be just paranoia. And they are not that decentralized as it may seem as BTC mining is controlled by two or three major mining pools if i am not mistaken? And each fork reduces decentralization even further.