When to communicate in the air?

I was on a short flight jumping airports yesterday to get fuel with my instructor and on the way back we were in between the two airports and he called in our position and that we were inbound to the runway. My question, why was it in the middle of the flight and not right before entering the traffic pattern? There was only a bit of traffic in front and it was about 500-1000 feet above us but it's heading was perpendicular to ours. Could it have been that he was warning the traffic of our position?