My guess is it's a mix of an 'NPM mindset' of how to deal with dependencies (e.g. 'the more the merrier'), and then including those dependencies as dylibs/frameworks instead of static linking, which kills any chance of dead code elimination (e.g. it doesn't matter if you only call a single function in a dependency, you still get the whole thing included in the app bundle).
yep, was able cut down an app from 70mb down to 10mb just by stripping out some 3rd party libs, and it turns out that most of the time only 1 or 2 functions were being used in a lot of cases anyways... i see this all the time...