The problem is, of course, that the other festivals just don't bring in the crowds as much as Pride. No one celebrates Greed because they're busy making money. Lust is popular but it's usually a small and private gathering. At the Envy-festival everyone steals everyone else's drinks. At Gluttony the snacks always run out. Wrath just pisses everyone off and everyone's to lazy to show up for Sloth.
(before you get your pitchforks out im bisexual its a joke chill.)