This is a problem with a lot of Teamwork classes. I played a Shaman for a brief period, and everything was pretty much based on "really cool things happen if you're next to my Spirit Companion". Unfortunately, despite basically opening every session with a reminder of this, I couldn't get any of the other party members to actually make use of those benefits. Sadly, perhaps 1/3 to 1/2 of my "and the guy next to the companion gets healed too" healing was wasted because people couldn't grasp the concept.
Rather than reminding them at the beginning, tell them "Too bad no one was next to my spirit, they'd have gotten X, too." when they've scattered to the four winds. And remember as well that you can put the spirit on top of a medium monster and have everyone in melee still be adjacent.