Smother Mothers Gender-Biased toward Boomerang Sons

A Reuters study  "Flying the Nest" showed how "smother mothers" (over-protective moms) welcomed their adult "boomerang sons" back home more quickly than daughters. A boomerang child is as the name suggests, a child who moved out, then returned to live back with parents. In this case, it seems to be gender-biased with mom and son relationships predominating over any other.

The 2010 film "Cyrus" explores the humor and pathos of smother mother love. The tagline says is well: "A recently divorced guy meets the woman of his dreams. Then he meets her son." Bouncing off from this film and the debate over boomerang sons, why are mothers quick to let adults sons live at home, while adult daughters fly the nest for good? Why let sons return over daughters? Why let kids move back, period? Is it healthy? Why Smother Mothers Welcome Boomerang Sons