You still need good solutions for bundling assets because network connections aren't free.
The approach you advocate can have adverse side-effects to web performance. It would help with the initial load time due to reduced initial JS, but if you end up loading a few or dozens of additional JS modules asynchronously you're talking about a lot of extra HTTP requests. Over HTTP 1 that's a big problem, and even over HTTP 2 each additional asset sent over a multi-plexed connection has overhead (~1ms or more).
Where's this ~1ms overhead for an additional asset on a HTTP2 connection coming from? Do you have a reference to a benchmark or something that demonstrates it?
IDK what calvin had in mind, but the client pull model you suggest can require a lot of round trips. Request a, parse a, execute a, request b, parse b, execute b, request c, parse c, execute c.
Of course, you could always do server push, but hey...that's pretty close to what a single bundled file is :)
The approach you advocate can have adverse side-effects to web performance. It would help with the initial load time due to reduced initial JS, but if you end up loading a few or dozens of additional JS modules asynchronously you're talking about a lot of extra HTTP requests. Over HTTP 1 that's a big problem, and even over HTTP 2 each additional asset sent over a multi-plexed connection has overhead (~1ms or more).