Initially the bikini divisions attracted girls who didn't really look like they trained, but were certainly willing to pay entry fees in exchange for attention and being called an athlete. Eventually the backlash became too great and the judges had to start rewarding "harder" girls in the npc amateur shows in attempts to add credibility to what most people saw As an insulting money grab.
The men's physique division started similarly, going from "pretty" and "athletic" looking competitors to guys who look like from the waist up they could be decent bodybuilders if they wanted.
So now that those divisions have actually evolved into (somewhat) respectable classes, they need more categories to keep the inflow of $. And yeah, it does appear to be getting ridiculous when everyone and their friend is an "IFBB pro" but you'd never actually know it if you're expecting a world class physique that should be unattainable by 99% of the population.