I get it. It's a HUGE culture shock. Family members can't uproot lives to live with them and even if they do, it's likely those family members also experience huge culture shock. Language barriers with the coaches and other players. Often times it could hurt their draft stock because they don't get playing time.
Look at Jeremy Tyler. 5* center. Had offers from every school in the country. Chose to go overseas. Played 7.6 minutes per game and then left the team to return to the US.
Dragen Bender got more minutes his rookie year of the NBA than he did with Tel Aviv Maccabi. As did Porzingis. Brandon Jennings never even topped 20 minutes per game in Italy.