Actually West, just goin strictly by sales #'s, the 57 Chevy was the least popular of the "Tri Five Series". which includes 55,56,57 Chevrolets.

1955-----1,776,653 total production

1956-----1,626,843 total production

1957-----1,561,655 total production

But when you compare its production #'s to those of the 1958 Cheverolet:
at 1,216,597, it prertty much clears things up.
The year 1958 wasn't a very good year for automotive production in general. But Soon after Chevy owners got their first look at the new for 58 design, you couldn't find a used 57 for sale anywhere.
I remember my Brother telling me that back in 1961, just after he purchased his like new turquoise and white BelAir coupe.