It’s less a result of market/no market than a result of multi/solo.
PoE is inherently designed as a multiplayer game (hence the online only), even if a SSF option has been added since.
While GD is first and foremost a solo game. There is an option to play coop, but it’s only an option: there are no dedicated servers and, most importantly, the balance is quite bad in multiplayer.
Multiplayer implies the possibility to get help from other players to overcome challenges by teaming up or trading. So the game can be a bit more harsh.
While solo implies you have to rely on your own strenght and drops to complete it. So the game is more favourable to the player.
To be noted that next expansion of GD introduce the possibility to trade a set item for another item of the same set or from another set.