YaST does seem to check dependencies when uninstalling. Try uninstalling perl, for exampl - you'll get loads of warnings about stuff that depends on it, with the option of uninstalling them, too. However, beware that, even if you say "cancel", it will leave the original package marked for deletion!
You are absolutely right. But I try to find packages that are not required by any other package. I give you an example: I installed gnucash on my system. Because of dependencies gal, guile, phyton, qt, slib, ... have been installed, too. But if gnucash is deinstalled, gal, guile, ... remain in the system. And there is at least one package that is not needed by any other package. I'm trying now to figure out how to find these packages. To find these packages manually is not possible. There are just to many packages. Fabian