Again, like said sometimes people really do have many real symptoms that could be 'something' but the cost of diagnosing to pinpoint is usually not realistic vs being able to treat the symptoms. Not saying I agree with it, but that's often why you're not going to get a life-changing diagnosis from a 15 minute GP visit.

For the many people who do have very real anxiety, often they are not conciously aware that what they're feeling is anxiety. Even if you've had anxiety for years you might not be. People especially do not understand how anxiety can cause very real physical symptoms, which are legit and can cause you pain and discomfort and could need to be treated. For example, if you have high blood pressure and heart issues caused by stress and anxiety those are very real problems that need to be treated, but there may not be a technical 'heart problem' to diagnose(which is a good thing! To your point it's really because of how much we(looking at you,America pay for health care that it almost feels more "worth it" to have something wrong than to be told we might have some symptoms and could legit not feel well but nothing dire is going on, because of the cost)

On a side note of unexplained symptoms, annual blood work really needs to be more affordable and promoted. Having just one value in your bloodwork off, something as simple as low B12 or iron or vitamin D(which is super common!), could cause a whole host of scary symptoms, but often it's not something a GP is going to casually suggest because blood work.