I've heard some people refer to all big rigs as "Mack Trucks", regardless of brand (Peterbilt, Kenworth, Freightliner, etc...) Why do they do that? Is it because Mack was really popular at one point?
I think your on the right track. Mack trucks were real popular in the 1970's till the other brands of trucks came about. Plus the idea of seeing the letters MACK in your review mirror was something not everyone wanted to see. Also seeing or having seen a car hit by a semi you usually think "Man that was one MACK Attack". Really I have no idea but this is just what I think.