It's a combination of Giroud's style and the midfield. The Everton game is a good example. During the first half he wasn't involved much because the midfield was really poor and the one chance he got he missed. 2nd half, we improved and the movement was better from him but he was still missing chances.
I think we'd get the best out of him if we had proper wingers either side of him. Troublesome players that can create openings with their dribbling. Gervinho has that ability and so does Ox. But we need a real upgrade on those two to get the best out of a player like Giroud. His movement can be good at times and he doesn't hide during games but he's pretty poor technically. He needs dangerous wingers either side of him and maybe a playmaker behind him to create space for him. He can't create space for himself.