Hospital systems around the country have started scaling back financial assistance for lower- and middle-income people without health insurance, hoping to push them into signing up for coverage through the new online marketplaces created under the Affordable Care Act. The trend is troubling to advocates for the uninsured, who say raising fees will inevitably cause some to skip care rather than buy insurance that they consider unaffordable. Though the number of hospitals tightening access to free or discounted care appears limited so far, many say they are considering doing so, and experts predict that stricter policies will become increasingly common.