My parents never dropped the last letter but always used a 'G" sound in place of a "C". I never knew why until I went to Sicily a few times and learned that the "C" sound is difficult for Sicilians to pronounce so they replace it with a "G' sound. My family is of Sicilian origin.
My Mom's people are from Abruzzi.. They drop the "A" at the end of Ricotta , supressatta,and "bracciola", the "i" at the end of "manicotti"; and tend to replace the "Cs" with "Gs". And it's "GRAVY", not "SAUCE"
My family was from up north. We never dropped the last letter either.