Just my personal opinion from using AC, MC and NM for many years. Back in the 40's, 50's and 60's home builders were often given the choice of armored cable or Romex by the EC. Armored cable was an upsell and if you were building a custom home, it's what you used. Romex was what was used in those cheap cookie cutter development homes, modulars and manufactured homes. But eventually builders stopped caring about something the buyers couldn't see and saw how they could put more money in their pockets. Cheaper, less experienced labor, rodent damage, staples overdriven, nails into the cable, ground to neutral shorts- cheaper to pass those problems off onto the EC if and when they happen than spending the money upfront to make sure they won't happen to begin with.
-Hal