Daily goals the game gives you to achieve for extra XP. Usually something like win 3 online matches, heal 10 teammates, or capture 2 flags. Basic skinner box methods to get the player on the game every day.

From the name I assume they're similar to the daily quests MMORPGs like wow assigned players back in the day ?

That is, tasks to accomplish once per day to get some rewards; it's a hook to increase the chance the players come back to the game

Why what looks like a non-persistent-world online game would need it I have no idea mind you

Daily quests. Missions that you can repeat every day for some recompense. Maybe they are always the same, maybe you get a different selection from the pool each day.

It’s MMO/Phone Game design that has bleed into every other games as a service to ensure engagement.