This is just my opinion, but I can give you some insights.
I think it was both a reason for competition and for unity.
On the one hand, the lands that are seen as having the greatest structures can feel more proud and more achieved- and this sensation is something that humans often seek.
On the other hand, the structures that "win" can be seen as a common, universal human achievement: a reminder of how much humans can achieve if they work together on one goal.