It really depends on if it’s a short term issue or a long term issue (from my experience). With your headache example, if it’s the first time having the problem (and it’s just a headache with no other symptoms going on), it may not necessarily be a sign that there is something else going on that is more serious/long term. So, they treat the headache and tell you to come back if things don’t improve or get worse. Then when you continue to have the headaches, they’ll look into it more. It’s far more likely that it’s just a short term thing than a long term/serious issue.