Why should you make or join a guild? I'll tell you why. Here in equestria, if you want to make money, you group with other traders, if you want to rule equestria, form a group of people who will be your guards, secretarys, and more. Limited only by your mind, you can invent a guild for almost any reason you can think of. Eventually your guild may become well known so that even its name brings joy or fear into the hearts of everyone who hears it, What you make your guild to be? That is your decision to decide.