The Spirit Realm

Is there a particular reason why knights get no 1handers or specialized 2handers at all until T3 this expansion. 2 tiers of no upgrades is kind of rough.

"Good" reasons? No. Just like there is no "good" reason why there isn't an EoA mask, and numerous other things.
Basically, the only reason I could see is "there wasn't enough room" due to a small amount of raids and they went with generic loot (Casters / Melee) for pretty much everything.

But then they went and put other specialized weapons on the tables anyway... which just leaves the whole situation as a wtf.

Itemization seems a bit strange in many areas TBH.

Hard to "catch up" if nothing drops that you can use, isn't it?

While I do agree that Tier1 having a knight weapon drop is unnecessary since that's usually the tier that drops generic everything, the fact that we have no knight weapons at all dropping until T3 (not even 2handers) really makes no sense especially when i am seeing the monk/bst equivalents in those tiers. The loot tables aren't supposed to assume you have been lucky in the prior expansion or have it completely farmed out.