Well it "makes sense" that no one gets headaches anymore, or they're uncommon. Presumably in a normal situation if you were getting a headache a remedy for it can easily be gotten. But there's a difference between the type of headache you get that annoys you for 20 minutes until the Tylenol kicks in and a massive, pounding, headache that's pretty much life-stopping like Picard was getting. (Often times a symptom of a bigger problem or condition.)
what Crusher found to be so odd ontop of the fact she couldn't get rid of it and it kept persisting.
And, yeah, it really should have been a clue to everyone that something "bigger" was going on here.