Using only a few KDE apps from a different desktop people install only the apps and kde-base/kdebase-runtime-meta as they are told by kde4-base eclass. But this way, people are not able to change the style of their apps, as the needed modules are in kde-base/systemsettings and qtconfig's settings are NOT respected by kde4. When people found out, that they can change their app's style using
they need to find the right package to install. If runtime-meta would depend on systemsettings people could change everything without hassle.
Steps to Reproduce:
Systemsettings is part of KDE Workspace, not Runtime.
KDE Runtime (so kdebase-runtime-meta) is set of programs and plugins that are needed by KDE *applications* to work.
It's not supposed to provide any Workspace functionality - workspace as something supposed to be used directly by users.
That being said ability for user to do sth without hassle is not the goal for KDE Runtime.
And even technically - kdebase-runtime-meta provides *only* packages that are contained within kdebase-runtime tarball (systemsettings is from kdebase-workspace).
I hope you understand :)