Comment # 9 on bug 948134 from Gabriele Mohr

The functionality of removing related files is still available in
"Options"/"Cleanup when deleting packages" but the setting isn't stored any
longer (same for "Allow vendor change").
The reason is to prevent unintentional deletion of packages (or installation
from a different repository in case of vendor change).
The libzypp default of these options is 'false' and the comments in
/etc/zypp/zypp.conf warn that "CHANGING THE DEFAULT IS NOT RECOMMENDED" because
of the risk of damage the system.