The reasoning I heard from a GP is: the more values you get back, the higher the chance of a false positive. A GP who has blood tested will do so based on your symptoms. Get the lab to do all the possible tests, and chances are at least one of them will be off but since you had no symptoms you’re going to have to test again because it might be a false positive. All of which takes a lot of time and creates feelings of insecurity with the patient. So where I’m from, there are no ‘check-ups’ in insured or government funded health care, you strictly react on symptoms. There are only checks for specific forms of cancer and you’re invited for this specifically. Don’t know whether this is the best way, but this explains the approach.