This is mentioned in the article, the fundamental problem is a capacity problem. If patients could be moved out of the ER department to hospital wards then there would be a greater ability for the ER department to monitor patients.
This is because beds are artificially expensive because hospitals deploy maximum-feature bed equipment and services, to avoid malpractice claims, and to increase billing.
There is a (somewhat artificial) middle ground in US hospitals where patients can be admitted for observation but still be considered outpatient.