CDNs are not 100% reliable. Best practice when using CDNs for static assets is to have a fallback if the asset requests fail. Many apps do this by falling back to a local copy of the asset when the CDN fails, but we cannot do that for all.js since it is unversioned and may change at any time. Therefore it would be quite helpful for Atlassian to provide at least one fallback url for all.js using a different CDN (not Cloudfront, where the current one is hosted).
We could build a mirroring solution ourselves but since this is something all apps should do it makes sense for Atlassian to provide it.