I mean, sure, that’s probably heavily influenced by the need for bundling for the frontend.
But it isn’t done blindly. Bundlers reduce the overall size of the code, either due to minification or tree-shaking (removing unused modules). It also removes the filesystem overhead of resolving and opening other modules.
Would bundling be useful in other interpreted languages?
I suppose you may count JVM’s compilation to bytecode as being very similar.
Ideally you’d only do this for live deployments (production and possibly pre-production or staging / QA). For all other testing, you would keep it unbundled.