When pokémon die, they are not gone forever. They become ghost types. Iceglow and Lynx even have a couple ghost types on their teams. Also the bond between a trainer and his/her pokémon takes years to fully mature. A trainer of the master caliber has an unbreakable bond with their team. While it is true that some trainers do not care for their pokémon properly, we make our best effort to show these wayward trainers the path to harmony with pokémon. If needed, then through battle.

Though it is true that the princesses would like their own pet Skittys, it is only through a respectable and experienced breeder. (Skitty breeding is one of the trickier processes due to the species being entirely female)