Is there even any reason the world needs more than 1 cryptocurrency? I know there are dozens (hundreds?), but they all effectively do the same thing, right? Allow decentralized currency that can be used for legal and illegal transactions.
Cryptocurrencies are tech products, various projects try various ideas. You'll have the initial blockchain idea from bitcoin, the privacy blockchain from monero, the programming contracts from ethereum, the decentralized exchange from stellar, etc.
I'm perfectly fine with that, I prefer to see people create new projects to test new ideas rather than to hear them complain bitcoin is not doing what they want.