I see your point, but game engines are usually a vast conglomeration of parts glued together somewhat haphazardly. If you're picturing a clean, well-executed design that programmers were given time to make perfect, that's a fantasy world. Time constraints make it almost a certainty that what you ship is a major compromise. I do think more people would play huge maps if they performed better, but that's not the main reason people don't play them. Most people can barely handle the amount of juggling and micromanagement in a standard map. Those of us who would enjoy the larger maps, even if performance was ideal, are in the minority I think. /shrug But yes, in Civ 5, long turn times became a major reason I stopped playing Huge maps.