Pre-ACA this scenario was common.
Pay-Check to Pay-Check employee is working for ACME Corporation. He gets his paycheck and insurance for the hard work and dedication he put into the job.
BAM, employee gets into a bad car accident and cannot work. Two to Three weeks later employee gets terminated because he can no longer do his job, insurance coverage ends. The former employee is offered COBRA, which is a possibility to stay on his policy at work, for about triple the price he was paying, because the employer no longer pays the portion they were paying. The employee loses coverage and is now diagnosed with a herniated disk that requires surgery. HE cant work, cant get private insurance because he has a PEC cant afford COBRA, and cant pay the Doctor because he cant work.
Under the ACA, this guy could get insurance, at a greatly reduced rate because he has no income... get his surgery and then go back to work.