I think dropped syllables in words can be lumped in with accents which are determined by where you live and what you pick up from the local manner of speech. When I came back home after 5 years in the service, my parents said I sounded like a TV news announcer in my speech. Now I'm back like the rest of the local yokels.
When I was active with military amateur radio service we were encouraged to pronounce the numeral five as fife.
We were ordered to pronounce the numeral nine as "niner" to distinguish it from "five" in poor transmission conditions.