Well what would you rather do when waiting in queue for a roulette or dungeon? Sit around doing nothing or make some progress towards your next level up? It’s better than open world farming, it’s quicker than fate grinding, it’s less traveling than daily hunts as well. The other better options all require waiting for a queue to pop so may as well do something while you wait.

That being said they’re side quests. I do them on alt jobs while waiting in queue because it’s something to do while I wait. Theres nothing requiring them to be done.