It’s because there are a LOT of followers who aspire to be carbon copies of these instamums - white, middle class, women who wear the uniform; dungerees/mom jeans/scamp and dude sweat, reebok classics, purple puffer jacket, blunt bob with thick fringe, oversized glasses and babe attached to hip and/or tit.
The followers have a disposable income and are easy targets to these types of things so they can post on insta wearing similar uniform with glittery chops and kids in a trolley living their best lives. It’s all a money making game.