I once belonged to a 'mouth fetish' group, so I can report that there are definitely people who have this paraphilia! If not immediately, with a little experience it can become very erotic! You anticipate the patient having to open wide, expose the moist interior of her mouth, show her uvula, and allow you to check her tonsils. If they're gone, I always ask, 'How old were you when you had your tonsils out?' (Note. I have also belonged to an 'anaesthesia fetish' group! The experience of having my own tonsils and adenoids out, at age 4, under ether, provided the stuff of - mainly - masochistic fantasy long afterwards!)
I enjoy the sight of the patient's uvula bobbing, especially the moment when she first opens her mouth and the back of the throat is set in motion. Then you introduce a curved tongue depressor and have her say a long 'Aaah!', and there is a real feeling of doctor-patient intimacy. Also, I agree with 'Jesterisniceguy' that the sight of a healthy set of teeth is most pleasant - and with 'Dr Dan' that the examination of the throat, teeth, gums and oral mucosa is a part of the examination that promises other delights to come!
In fantasy, you can think of it like this. The two tonsils are like the female labia. When she shows you her tonsils, it's like her saying, 'I'm co-operating!' (And if the tonsils are gone, it's like her saying, 'As you can see, I'm experienced! Keep examining me!') By extension, the uvula is like the clitoris, another come-on! (Hmm. I think I have detected in young adult male patients - whom I also enjoy examining - a possible correlation between uvula size and penis size!)
Finally, I would add that all medfet exams are the more pleasing if there are proper lamps and instruments. Just the sight of a well-appointed exam room is a thrill to some of us!