It's casual crossword solving vs competing at Jeopardy. Civ games last a very long time (depends, but e.g. 10 hours) and are extremely slow paced, which plenty of people enjoy. Games like Age of Empires punish you for daydreaming for mere seconds during a 30 min match.

One of the appeals is they aren't real-time.

Turn-based games are more complex because having time to make your moves allows you to consider much more than you could in real time.