Because one doesn't actually use `AixObject` as a provider. The original author had it as a base class for providers of other types like user or group, which should override `lscmd`. Because of dynamic dispatch, we'll get the `lscmd` from the more specific provider.  See https://github.com/jeffweiss/puppet/blob/a27f3dc427baa56f68020f4daee52c35ea4daa7a/lib/puppet/provider/user/aix.rb#L98