The C melody was part of the series of saxophones pitched in C and F intended by the instrument's inventor, Adolphe Sax, for orchestral use. Since 1930, only saxophones in the key of B♭ and E♭ (originally intended by Sax for use in military bands and wind ensembles) have been produced on a large scale.
Further down is says this:
However, it is important to note that production ended for purely financial reasons, and not because of any inherent flaw in the design or poor manufacturing standards
Why was the C melody never produced after this and E♭ and B♭ produced?