This world isn’t your normal world. The climate treaty force down all the countries all over the world to drastically reduce their energy consumption. This ban put heavy blow on mechanisation that humankind was employing. The worst hit industry was automobiles. Soon after the ban on oil the automotive started disappearing from the road. Their place was taken by old horse cart.
But to make situation worse a pandamic decade ago wipe almost all the population of horses. Now there was carts but no ponies to pull them. The smaller and poor countries started using human, specially women to pull their carts. Soon this practice spread all over the world.
The women being to be enslaved and forced to be a pony became popular. This rampant pony slave was opposed by many faminist groups. UN was forced to put ban on forced ponification. But till now ponies not only became a need but became glamourised specifically in teen girls who were brainwashed through media to become pony. The sedist men in power allowed volunteery ponification. The research grew on this, a new drugs, training method and schools started to train ponies and make better ponygirls.