Sometime I think it's an attempt at game management, slow the opposition down if they have momentum etc. Certainly looked like that against West Ham.
He needs to stop because more often than not it hands momentum to the opposition. Case in point, him going down gave us one less as Swansea broke and Lascelles had to bail us out with the clearance.
It was absolutely awful going down in that scenario unless he was badly hurt. Could easily have been the difference between winning and losing the game