Why? It’s tucked way in the corner under your energy globe. Combo Points show up front and center, sensibly positioned right where you’d quickly glance for buffs and cooldowns.
It’s almost as dumb as Necromancer’s Minion tracker being next to their Essence instead of tracked on the Raise Skeleton icon.
It’s like every little aspect of the game was made by a completely different person, and none of them ever communicated what they were doing.