I can't think of any reason why they should be off-topic. I stand by my statement I made before that we really can't answer behaviour questions when we don't study animal behaviour, but then decide not to answer medical questions because we don't study medicine.
We definitely aren't a replacement for visiting a vet though, so I think it would be good if we put it in the help center, or made an announcement on meta that any medical advice is supplemental to visiting a vet. It would be really nice to have a pop-up when selecting the health tag that they should consider visiting a vet.
I think what we need to do, is figure out what isn't working about these questions, and try to figure out a way to fix that problem.
The common problems I've noticed with medical questions are:
They don't include a picture:
If we can't touch the animal, then we need to see it. We should get stricter on these questions and instead of asking for a picture, require one. I put together some posts under What common information should a question poster be expected to provide about their pet? for what I think is required in different types of questions, one of them is for medical questions. I think it would help if we could have items listed that are a minimum requirement for what's needed in a medical question.
They try to ask multiple questions at once:
A lot of times with these questions, I see the final question being asked is really not clear. There are two types of questions I've noticed.
Where the person is scared or stressed about the condition, they tend to ramble off questions at the end. "What if it's this condition, should I do this? Should I be worried? What if it gets worse? Is this normal?"*
Questions that follow the format of "Is X true or normal?
We need to be more strict and enforce one question per question block.
We should try and figure out ways to make these questions more clear:
I think what this all leads to is a bunch of questions that aren't really clear enough that people feel comfortable answering, but no one votes to close them as unclear because technically they aren't.
The problem is that makes these questions just okay, and okay questions are boring. If we want to keep the site interesting, we need to have more great questions than okay questions.
I don't know if we can completely get rid of these types of questions, because sometimes they do work pretty well. I'm pretty biased since it's about reptiles, and I answered the question, but I think that What is this dull patch on my bearded dragon?What is this dull patch on my bearded dragon? turned out to be a good example of how these questions can work. I had to ask for a picture, but after that was added the question had everything needed to diagnose the condition.
Personally, I would like to see some of the questions changed to be more like "Is X a symptom of Y?". But in order to do that, I think we would need to decide if we require some sort of prior research done on these types of questions.
If we can set up some minimum requirements for these questions, whether it's requirements for what's needed in the question, or prior research, or both. Then we can start to close the not so great questions for not adhering to the guidelines. (It would be great if we could have a new close reason specifically for not having enough details, but I think we're supposed to use the unclear vote for that.)