If we're going to talk about linux packages, aren't they often written in languages with amazing optimization skills? If I write some C99 code that uses a gigantic library but I only use like 2% of it, my compiler will cut out the 98% my code doesn't use, so libleftpad sounds like an awful idea. That's one reason why packages on linux distros aren't too big.
But I'm talking about iOS apps where, as others have pointed out, the available optimizations suck[0], and as such, I think that having libleftpad.o included in everyone's iOS apps isn't a big deal (note that iOS doesn't really have a nice way to create libleftpad.so anyway AFAICT because all code for your app is supposed to be sandboxed so no one else can mess with or use it). I agree that it would be really cool to just cut out the 98% of $GIGANTIC_LIBRARY that isn't used at compile time, but since Objective C doesn't seem to have that now, I think small things would be a really nice way to give users more space on their phones without removing features.
Not necessarily. Distributions have to build everything, and in openSUSE we have an integrated build system[1] which has a lot of very useful features (rebuild when dependencies are updated, and automated QA runs before releases). Those features require you to have all of the dependencies of a project in an RPM package. Even if you don't end up shipping that package, the package is used for tracking security issues and backports and so on. You can't pull anything from the internet during a build, you have to depend on your BuildRequires.
Now take any average JS application that has over 800 dependencies. Ruby was already bad enough with ~80 dependencies, but adding another order of magnitude is just not maintainable. One of my colleagues gave a talk at LCA about this problem[2].
[1]: https://build.opensuse.org/ [2]: https://www.youtube.com/watch?v=4ua5aeKKDzU