"My car has no steering wheel", though, so isn't it related to how many you'd expect?
Exactly right. Op uses “snails have no legs” because most things have 2+ legs or none. But snails do have one foot. If there was a snail without a foot, you’d say “this one has no foot”
I'd say steering wheels are "normally capped at 1"... although I recall one distinct occasion where I expected two steering wheels, in a training car for new drivers. Alas, it seemed the local school-district could only afford a car with a second brake-pedal for the instructor, which did very little to help my anxieties.
So my first time behind the (singular) wheel and they told me to pull onto a major street next to the school, without even doing circles in a parking lot or anything. I guess they just expected most students had already done some illicit/private driving? Anywho, it was more stressful than any rollercoaster and I had shaky legs when my turn was finally over.
(Then I put an onion on my belt, as was the style of the time...)