It has a *little* to do with game design. They chose to depend on Steam servers / GOG servers, rather than choosing a server ecosystem that would be cross-compatible. They also neglected to include a direct IP option. There are undoubtedly reasons for these choices - perhaps even good ones - but it's not as if when designing the game, they didn't have the option to include this stuff.
They also don't make this restriction clear to anyone who isn't as 'educated' about the server situation. Thus my friend now needing to apply for a refund on GOG.
Well said!
I've waiting years for a multiplayer GalCiv, now I talked my friends into joining me in buying it and we (after the fact) discover that the ability to connect for multiplayer is extremely limited!
As a software developer, I can certainly understand Stardock's decision. However it should have been clearly stated so any purchasers wouldn't be rudely surprised by this limitation.