Why are there so many cryptocurrencies?

Believe it or not, but there are about 3,000 cryptocurrencies in existence. Most of them are tiny in size and it is doubtful if they serve much of a useful purpose. But there is a fair amount of large currencies. All of the top 10 have total market values of more than $1.5 billion.
The 3 major cryptocurrencies Bitcoin, Ethereum, and Ripple, all have significantly different purposes, and the same can be said for many of the other larger cryptocurrencies. Some are designed for payments and some are designed for transferring information, etc. So, carefully pick your cryptocurrency designed particularly for your own purpose.