Say you're 40 and you get a positive PSA result, maybe that means your risk of having prostate cancer has gone from (for illustrative purposes) 0.1% to 2%. That means the next step is "what do you do to someone who has a 1 in 50 chance of having prostate cancer?", and the answer is almost certainly not a biopsy or anything majorly invasive. The answer might be a finger up the butt, an MRI, monitoring for symptoms, repeat the test in a year, etc.

The problem is that patients aren't used to handling these ambiguous results from tests because we don't do much routine testing, and doctors don't want to face the potential consequences for getting a positive test result and recommending against invasive treatment. However, in many cases, a test would still tell you something useful even if it won't directly be used to escalate to a more invasive test or treatment.

For example, if a routine blood test shows prediabetes (which has happened to a few people I know when having blood tests for unrelated matters), you won't get any treatment for it, but you may be referred to a dietician and have a fire lit up under your ass to make those lifestyle changes you've been putting off.