I'd say steering wheels are "normally capped at 1"... although I recall one distinct occasion where I expected more two steering wheels, for driving training. Alas, it seemed the local school-district could only afford to put in an extra 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, 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...

The exceptions are always fun: https://imgs.classicfm.com/images/41395?crop=16_9&width=660&...

In France, training cars have only one steering wheel, and the instructor is perfectly able to drive the vehicle by steering with his extended left arm.

This is standard in the US as well, probably almost everywhere. But as the comment says, there's always an exception.

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”