Sure you can use external repositories. But why bundle old packages when everyone then has to use external repositories to not get really old versions?
* QA to make sure all the interdependencies aline correctly
* making sure the upgrade process runs smoothly, and that going from version X to version Y of some package is well-tested
It also depends on the upstream release cycle of the software package. The distro may wish to use the LTS version software (e.g., OpenJDK, OpenZFS, Django, Zabbix) but developers may wish to be more bleeding edge for new functionality.
* QA to make sure all the interdependencies aline correctly
* making sure the upgrade process runs smoothly, and that going from version X to version Y of some package is well-tested
It also depends on the upstream release cycle of the software package. The distro may wish to use the LTS version software (e.g., OpenJDK, OpenZFS, Django, Zabbix) but developers may wish to be more bleeding edge for new functionality.