He would have lost rematch with Hendricks. GSP definitely got the worst of it physically versus Hendricks. It became quite convenient to retire rather than finish clearly on top like Khabib. When fighter not in Top 5 at MW became belt holder it was quite convenient to un-retire. He would have lost defense versus anyone in Top 5 at MW after he won the belt. It was quite convenient to retire again.
At least Ronda had motivation to take the higher paying Hollywood job after losing badly on two fights. She clearly didn't retire to avoid opponents.