"some people apparently exist who need to support ES3 - think IE6/7, or extremely early versions of Node.js"
Seriously what kind of business today needs to support ES3 browsers? Even banking sites should refuse to run on such old devices out of security concerns.
This is 100% teams who set up their build tooling back in 2015 and haven't updated since. There's plenty widely used apps and libs that date this far back, and back then, IE8 compat was considered pretty important still, esp for products targeting enterprise/government customers.
Upgrading eg Webpack and Babel and polyfill stacks and all that across multiple major versions is a serious mess. Lots of breaking changes all around. Much better to just ship features. If it ain't broke, don't fix it!
No one really does, but there's one particular individual who keeps pushing to support things like node 0.3 and who also maintains all those low level intrinsic packages.
I remember reading somewhere that Deutsche Bahn is running Windows 3.1 for something still?
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