When Babel 6 came out, it was hard for a lot of packages to upgrade because it was essentially an entirely different category of thing than Babel 5. So what happened was that some packages upgraded, and some didn't — at least not straight away.
Some projects took the prima facie enlightened view that packages should expose untranspiled code, so that the consumers of that code could determine for themselves what needed to get transpiled based on the environments they supported.
That was a costly decision. If I was the author of an app that was using Babel 6, I couldn't import a library that was still using Babel 5 and shipping untranspiled code (because the configs were completely incompatible), and vice versa. Frankly, it was a bloody nuisance. We are bad at anticipating these sorts of issues. It will happen again at some point.
Adding a few extra bytes to pkg.main
or pkg.module
is a small price to pay for things just working. As well as avoiding the aforementioned headaches, it means that your