I think it's down to two things:-
a) they think bigger means better
b) they want to stifle progress and force people to buy boosters at £10 pop
With Assassin's Creed going full live service in the future, it's only going to get worse I reckon. If they weren't trying to screw users into spending more money to reduce the monotonous agony, they would've included XP scaling options where users could curate their own experience based on how much time they have or wish to play. If they didn't alienate players this way then more would spend money on DLC but they are obsessed with nickle and diming their in-game stores.
Ubisoft have phasing out narratives from their games now and focusing purely on live services of the stinking F2P nature so I dread where this franchise will end up. All the staff at their disposal, all that technology, all that money and their games are the same generic reskinned crap over and over.