The announcement, made via Twitter and Fortnite’s in-game news feed, said that improvements to aim assist necessitate the scheme’s removal. The legacy settings date to an effort last fall to balance matchmaking across platforms and controller types.
A PC’s mouse and keyboard, generally speaking, is quicker and more accurate than a user aiming and firing with a gamepad. Aim assist was supposed to close that gap for gamepad users, but some discovered a way to track players through walls, smoke, and other obstructions.
When “Use Legacy Look Controls” leaves the game on March 13, players who still had that setting active will have their sensitivity settings reset to the new defaults. Players who wish to preserve those settings may do so before then by using the “Copy from Legacy” choice in the Controller Options menu, and then toggling “Use Legacy Look Controls” off.
Fortnite’s patch at the beginning of October tried to address matchmaking across different control schemes. Legacy settings were made available at that time, although Epic tried to encourage players to give the then-new schemes a chance. but fans weren’t really going for that.