The EHR mandates were very loose and had long deadlines. Hospitals had plenty of time to buy or build whatever they wanted. But it would be ridiculous for almost any hospital to develop something in house; they don't have the engineering resources or a core competency in software development, and it would be a huge duplication in efforts. Some hospital administrators like to think their institutions are unique and special snowflakes, but the reality is that most of them are the same and would operate more efficiently with standardized tools and processes instead of something customized.

While a single hospital might be able to operate reasonably well without an EHR that's just no longer sustainable in the broader healthcare ecosystem. Hospitals can't be islands. They have to be able to share data with payers, public health agencies, other hospitals, outpatient clinics, researchers, etc. Doing that requires an EHR now.