I had a Tongan roommate who shared that in Poly culture everyone is expected to chip in financially to help the family. That includes the young men.
Since most Samoan/Tongan families are working class/poor the lure of $$$$ from the P5 is tempting especially when your family is in need. Nike $$ at Oregon has had to play a role.
For most white LDS families this isn't an issue. But for immigrant families BYU just doesn't cut it in terms of "support".
I don't fault Poly players & families for looking elsewhere because of the financial benefits.