Probably because javascript engines (since 2008ish) are constantly improving and each new ES version adds new specs/features so there are opportunities for the

Probably because javascript engines (since 2008ish) are constantly improving and each new ES version adds new specs/features so there are opportunities for the smart, brave and foolish to build libraries and frameworks for these. I think it's good that there is so much fervour around it. Time and use will flush out the things that don't work and we'll be left with the bits that do (well mostly)