Why are the flaperons on the 787 located so far in-board?
Quoting the answer @fooot linked to:


  At high speed, the outboard ailerons are locked and all roll control is achieved by deflecting the inboard ailerons (and spoilers, if needed). This helps to reduce wing torsion and twist.


Yes, roll authority will be larger once the force is applied further away from the fuselage (/ roll axis), but the cost at which this comes (wing twist) is larger than that benefit.