[colonwqbang]

A native compiler also optimises the code. A native static linker also tries to omit unused library data and code. It's absolutely not the case that native devs don't care about code size (we do!)

I guess Javascript uses a slightly unusual executable format, text instead of binary. Otherwise, it seems like very much the same thing?

[crabmusket]

I'd say that bundler design is less influenced by the format and more by the requirements of delivery over the web. Native code is not downloaded each time the user opens the application. Tons of web infrastructure and complexity is aimed at solving the problem of "user lands on page for the first time, it must be responsive as soon as possible."