And my car senses rain with ease. I wonder if your car needs some kind of service, because the car senses rain fairly well, though what would I know, living in California.
This is signal detection theory. There are four conditions, as illustrated here:
The "hit" and "correct rejection" cases are ones where the car gets it right -- it runs the wipers when there's rain and does not run the wipers when there is no rain, respectively. The "miss" and "false alarm" categories are ones where the car gets it wrong, but in entirely different ways, and it's important to consider both cases. In my experience, my Model 3 rarely falls into the "miss" category (but see below); however, it often experiences false alarms. The wipers will sometimes start up for no apparent reason. My suspicion is that the system is misinterpreting dirt/dust on the windshield, perhaps interacting with glare from the sun, as rain. Sometimes using the washer fluid squirter can clear up the problem. Other times I've had to disable the wipers.
Also, and more importantly, although I said that my Model 3 rarely enters "miss" category, in this case it's more complicated than that, because rain isn't a binary thing. Rain can be anything from a light mist to a dangerous downpour; it can be steady or variable; it can be warm, freezing, or turn to snow. The appropriate wiper speed varies depending on these factors. In my experience (mostly in New England, but with road trips westward as far as Cincinnati), my Model 3 often runs the wipers at too low a speed. This can (rarely) include what would be called misses in SDT, but more often it's just that the wipers end up running at one, or sometimes two, speeds too low. When rain is still very light, this can be handled by pressing the manual-wipe button on the left stalk, but this solution is annoying at best; and when they're running too slowly with heavier rain, it's necessary to fumble with the awkward on-screen controls to manually set them higher. This is, in fact, my #1 complaint about the Tesla's controls. I'm not alone in these observations; many people have the same complaint, particularly those who live in areas that see lots of rain. Thus, I don't think it's a matter of my car needing service; it's one of many examples of Teslas being designed in southern California for the driving conditions in southern California, with conditions in other areas seeing little consideration.