Making user friendly games doesn’t mean making them easier. Regardless, developpers still often make this mistake. The purpose of games user research is to ensure the player’s experience matches the designer’s intent. This can lead to simplify interfaces and remove unwanted challenges from the game, such as confusing controls. It does not imply removing any meaningful challenge though.
To illustrate that games user research can actually lead to making games harder, I will tell you the story of Olympus Naumachia. Game user research made this game quite a bit harder, yet less complicated.