Well, just using the examples the OP used, the 130 and 140 divisions existed a long time before other junior/super divisions, having near identical recognition as world championships, with the first period being from the early 1920s to the early-mid 1930s, then brief recognition in the late 1940s before the full-time establishment of the divisions from the end of the 1950s. Not sure what the reaction at the time was to those divisions but historically they tend to be treated as legitimate world titles. Fighters like Tony Canzoneri and Barney Ross are considered three weight world champions based on their junior welterweight title reigns (having simultaneously fought for the lightweight and junior welter titles in the same fight). The super bantam division was technically established in the 1920s (at least there were some fights for that title in 1922 and 1923) but it was a very brief period before it was dormant for over 50 years and the division was established full-time from 1976. I believe the super fly/junior bantam division was also established in the 1920s, but a world title fight wasn’t contested until 1980. I think the main reaction to the additional junior/super weight classes was predominantly ‘Why?!’. If you look at the ‘original 8’ the jump in poundage makes a lot of sense: Flyweight (112) to Bantamweight (118) is six pounds; Bantamweight to Featherweight (126) is eight pounds; Featherweight to Lightweight (135) is nine pounds; Lightweight to Welterweight (147) is 12 pounds; Welterweight to Middleweight (160) is 13 pounds; Middleweight to Light Heavyweight (175) is 15 pounds; Heavyweight was anything above that until Cruiserweight came in, first at 190 pounds (so another 15 pound gap between divisions) before the maximum weight was shifted to 200 pounds (a 25 pound gap). So there was an incremental increase in poundage between the weight classes (There is some nuance in terms of the individual histories of these divisions and the exact poundage that I’ve left out here for the sake of brevity, but as a general point, I think it still holds). With the full-time establishment of the junior and super divisions, those more balanced increments disappeared and the gaps between weights became more arbitrary.
