Well, United Healthcare, Humana and Aetna all say their decisions are based on loss of money.

NBC News  August 16
Reuters

"Aetna, the No. 3 U.S. health insurer, on Monday said that due to persistent financial losses on Obamacare plans, it will sell individual insurance on the government-run online marketplaces in only four states next year, down from the current 15 states. 

Aetna's decision follows similar moves from UnitedHealth and Humana, which have cited similar concerns about financial losses on these exchanges created under President Barack Obama's national healthcare reform law."

"Only about 11 million people have signed up through the exchanges, about half as many as expected."

http://www.nbcnews.com/business/business-news/aetna-pulls-back-obamacare-health-insurance-plans-2017-n631656