It's rather that our Python maintainers/foundations team don't want python2 dependencies on the default install. As we install apport by default, it can only depend on python3 stuff, so Barry asked me to make the python2 bits optional. And indeed launchpadlib is not needed for most apport operations (its main purpose is to file bugs), only if you invoke it as apport-collect. So the default install with python3 is still mostly fine.
It's rather that our Python maintainers/ foundations team don't want python2 dependencies on the default install. As we install apport by default, it can only depend on python3 stuff, so Barry asked me to make the python2 bits optional. And indeed launchpadlib is not needed for most apport operations (its main purpose is to file bugs), only if you invoke it as apport-collect. So the default install with python3 is still mostly fine.