I don’t understand why challenges arent in the game? This is one of the few areas i think Halo 5 has moved backwards in comparison to 4.
They make it more enjoyable to replay the campaign(especially on legendary with skulls on) due to it progressing your online character, and it can spread the population to lower populated game types.
It just doesn’t make much sense for 343 to take them out.
These would be a great opportunity for req points to be given for completing daily/weekly objectives. Say play/win so many certain matches in a set playlist or certain campaign story missions with “x” skulls active even if you have not unlocked the specific skulls just for more of a challenge to the player