I imagine it's difficult to keep making runs when he knows people aren't looking for them.
Once we have a coached style of attacking play, rather than the moments fc we have right now I think it will be way easier for him. In other teams they have link up players who's first thought it to try to find the striker. I remember one of the matches we lost earlier in the season (I can't remember who) the opposition player said "As soon as I got the ball I looked up and played the pass without thinking - I know he will always make that run".
None of our wing options (Rashford, Garnacho, Anthony) think like that - their primary thought process is to look to cut inside and secondary is to pass it backwards if that isn't on, in the hope of getting it recycled back to them when it might be easier to cut inside.