Yeah but the problem is that people don't just use a single webapp all the time. We all browse and go to many different websites, which all have payloads that they want us to download and run. So in practice it ends up that we're re-downloading bundles constantly, many of them which have the exact same libraries, but because they're bundled and minified, they're not cacheable so we have to fetch them over and over again.

Don't believe me? Check this out: https://tonsky.me/blog/js-bloat/