Comment by louiskottmann

I think this is mostly historical baggage unfortunately. Every codebase I've ever worked in there was a huge push to only use native ES6 functionality, like Sets, Maps, all the Iterable methods etc., but there was still a large chunk of files that were written before these were standardized and widely used, so you get mixes of Lodash and a bunch of other cursed shit.

Refactoring these also isn't always trivial either, so it's a long journey to fully get rid of something like Lodash from an old project

This has improved recently. Packages like lodash were once popular but you can do most stuff with the standard library now. I think the only glaring exception is the lack of a deep equality function.