Because.
really.
when the fanbase can come up with ideas like This or this (based on Greavers and Silkwings respectively; credit to Caicaibia and Malakym respectively), you know there's potential.
And it's not like a case can't be made for more armor types; the armors could be anti-enemy types like the chroma or support subclasses of weapons, or heck - even just a Mad Bomber-esque armor for swordmasters and gunners would be cool.
(and how can you resist that cape on the greaver set. how. C'mon OOO you know you want to make more armors. Give us a Trojan-themed armor that isn't a joke)
I want to attribute stats all over that thing.
"a Mad Bomber-esque armor for swordmasters and gunners"
MadB is one of the few things bombers still have as an advantage. You may as well say there should be a bomb version of Blitz. Besides, we already have this.