One potentially compelling reason is dependency resolution. You can’t express Cargo-style “collect _requirements_ for all dependencies, and then pick the minimal set of dependencies which satisfies all requirements” with just urls. You potentially can encode fancy constraints for each specific dep into an url, but you can’t have an algorithm which globally looks at the set of dependencies. If you want that use-case, you’ll need some extra tooling which reads constraints and writes the import map.
OTOH, it’s not clear if fancy constraints solve more problems than they create.
Notably, if the only constraint is `^x.y.z`, than the gready, expressible-via-urls algorithm of always selecting the latest semver-compatible version yields the minimal solution.
Yeah that's fair. Personally I'm not too worried about that use-case, but it is something that would be tricky to solve with URLs that get treated as black boxes
