Patients globally think that procedures are inherently good, it's not inherent to the US system.
I'm a doctor working in a government funded public healthcare system, where there is every incentive for the system to NOT do investigations and procedures where there is a poor evidence base. Yet we still waste $BILLIONs every year on them and the majority of this is driven by patient demand.
I frequently get patients where the evidence is for intervention A - that requires the patient to do N amount of work (for example physiotherapy, strengthening exercises) with slow, but real, results. After 15 years of medical practice I can honestly count on one hand how often a patient has genuinely taken an interest in this approach and committed to it. This sentiment is shared across colleagues. The vast majority of patients want a 'quick fix', even when there is no evidence that a quick fix exists.
So they push for intervention B, creating long waits for patients who would genuinely benefit from seeing the interventionist who offers B, resulting in worse outcomes for that cohort.
As the system is free at the point of access patients can simply 'doctor shop' and see as many doctors that are needed until they get one who agrees that intervention B is what is required.
I think it comes from an assumption that lay people have that the body is a machine and if a part of it is broken it can simply be 'fixed'. The truth is, is that the human body and biology are messy. We can't even define broken in a lot of cases, you can have two people with the same finding on a scan and one is in pain and the other is completely symptom free. People find this concept really hard to understand, but most of biology is happening on a microscopic level for which we don't have tests and scans, which again people find hard to accept, that we do not always have an answer. Human biology is not a solved science, not even close. There is also the whole complicated factor of human perception.
Two people can have the exact same experience but have completely different feelings and ideas about it. For one person, post-nasal drip maybe completely distressing and make their life miserable. Another person may have the exact same level of post-nasal drip but it does not bother them at all and they live their entire life with it without ever consulting a doctor. So what partly drives health demand is a patients tolerance and perception of their symptoms, which can change over time.