So why the heck is there 653 currencies ?

Personally, I hope there will be even more.
S. Nakamoto democratized the creation of monetary system... We can't stop people from creating, copy/pasting. And that is what they do with Bitcoin source code. The best way to hedge this "creation" is not to have the whole planet using solely the Bitcoin protocol (This is a sort of centralisation to me) But it is to let everyone create their own monetary system.