I have noticed the following reasons.
1 Home is home no matter how comfortable you are outside of it. So once a decent life becomes affordable for people in their homeland they prefer to choose it and return. Much depends on the country in which one is settled.
2 Many people living abroad are apprehensive about the foreign culture which they fear will lead their children astray. A few find it sufficient reason to return.
3 There are people who wish to return to the native land and live their last days there after retirement
Joseph M.j., Lived in U S for About 2 Years.