It mostly boils down to the used game engine: Civ 5 is written in a custom engine (LORE), where you can choose which platforms to support. Other engines might m

It mostly boils down to the used game engine: Civ 5 is written in a custom engine (LORE), where you can choose which platforms to support. Other engines might make it easy (Unity), hard (Unreal), or impossible (Frostbite) to support Linux and Mac natively. Platform support is of course an argument when choosing an engine.