I love the extravagant architect of ancient lands. Why build a wall with eight arches when one will allow for entry and exit? Perhaps masses of people desired entry for an event? I don’t think the population of Volubilis warranted the 8 entrances. I think the arches exist because the Romans wanted to create something grand, wanted to design a structure worthy of an emperor, wanted to flaunt their wealth. I think the arches exist because the Romans loved beauty, beauty built to reflect the grandeur of their many gods.