Obamacare premiums have been going up due to the medical costs of the previously uninsured

http://www.nytimes.com/2016/03/30/us/politics/newest-policyholders-under-health-law-are-sicker-and-costlier-to-insurers.html

People newly insured under the Affordable Care Act were sicker, used more medical care and had higher medical costs than those who already had coverage, the Blue Cross and Blue Shield Association said Tuesday in a new study of its policyholders.

Because insurers’ premiums have to cover their medical expenses, the new report helps explain why Blue Cross plans have sought, and insurance commissioners have approved, substantial rate increases in many states. Another round of rate review is about to begin, with insurers generally required to file rate requests for 2017 in the next two months.

New insurance policies are often more generous and comprehensive than individual policies sold before the health care law. The new policies must, for example, cover maternity care and mental health and substance abuse services.

Whether you think the uninsured should be covered, which is a normative question, why does anyone think that moving to a single payer system will be cheaper at the overall system level if you cover MORE people for MORE benefits with FEWER cost controls (deductibles, co-payments)?