Perhaps to reassure people that Harry and Ginny didn't get married, settle down and have children immediately after the war. The oldest of Harry's would be what, 12? 13? So there's at least five or six years of relative freedom in there, and enjoying the new world. Perhaps that's when all the rebuilding and restoring of order and the workaday world took place, and they all only settled down to have children when it was safe and ordered and just as Ron had imagined it to be all his life.