Ya this is a problem IMO. It is not helping the profession to have retired, more expensive teachers taking on call jobs from the new teachers.
On first glance it might seem a veteran teacher is taking a job from a new teacher, but really the veteran teacher has vacated a job so a new teacher can move from subbing to full time teaching. It is much better for younger teachers if the older teacher retires a bit early and then subs to supplement his or her income instead of hanging on a few more years.