Inspiration from a couple of other MN threads....
Although the absent parent may not have been around at all, they still could hold PR for the child. If say me and DS were in an accident, ex (who has zero contact), could be the person who decides to pull the plug rather than my family who know and love DS.
Or if I popped my clogs with no will, life insurance payable to DS would be under the control of ex due to PR.
Even just a normal, I've brought him up all this time why should you be allowed to reappear x amount of years later and challenge for contact?
So, AIBU to think (with a few rare and extreme exceptions), absent parents should lose the right to contact/PR etc after a sustained period of lack of interest?