What comes around, goes around.
You are just evaluating the current life events from physical realm.
Have you ever considered that maybe they helped you in other past lives?
Or if you had a soul agreement to help them in such way?
Or if your destiny was not having those jobs? because your life lies in a different path?
Yes, I agree that life seems a mystery.
However, if we take blinders off, everything becomes more clear and logical.
So, you helped them in this life. They will be there to help you in next lives.
Many life events, especially relationships with other souls, birth, and death are predetermined well before we came into this physical realm.
"Man cannot discover new oceans unless he has the courage to lose sight of the shore". - Andre Gide