I assume that Jesus healed people to prove who he was, to get across his message and to show compassion. If those were his reasons - would it not make sense to heal more people?
If Jesus' abilities were limited in some way, then possibly that might provide an explanation. But I would assume Christians would not see Jesus as limited in any way.
Mark 6:5 is interesting "And he could there do no mighty work, save that he laid his hands upon a few sick folk, and healed them. And he marvelled because of their unbelief. " - perhaps he could only heal those that had faith?
I know if I had the ability to touch people and heal them I would set myself up to process as many individuals as possible - I'd get them to queue up and see them on an industrial scale.
If I only had a few years I'd probably focus on terminal illnesses and children. If I wanted to get my message across I would throw in a few kings here and there. My message might be for the poor and downtrodden, but getting a few people with power on-side might be beneficial - especially if they came and followed me - being God I'd know who to help. I might find a few historians to heal as well.
On the face of it Jesus' approach seems to lack imagination and foresight - unless he was limited in some way.