because in the last 3 years they were doing shit like, oh i don't know:
Adding all of the Vaal content
Adding Masters and crafting
Adding a fucking ton of new skills and auras and Heralds
Adding literally fucking hundreds of unique items
Adding Act 4 and all of the 2.0 content
Adding the mechanics of Divination cards
Adding new maps
Completely fixing Desync for the majority of players
Overhauling the passive tree
Adding Jewels
Creating support for Brazil and Russia
Creating new fights for challenge leagues
Adding Ascendancies and the Labyrinth system, which required substantial rebalance of classes
Adding multithreading to the game's CPU process
Adding Prophecy and all the voice acting and systems associated with it
Creating the Atlas for the endgame
Adding new end-game content
Rebalancing everything every single fucking time
Working on DX11 upgrade
MOST PLAYERS don't even experience trading via poe.trade. Most players never fully engage in trading. It's not something that they can just slap together and release it along with a challenge league or whatever. Shit takes extensive design and testing time, and they clearly have prioritized that elsewhere while they roll out trade improvements in several successive waves. They've said so, MULTIPLE TIMES.
So what don't you understand about my comment?