The Pies died out last generation, Rocksteady and Gemswirl Pie never had a chance to birth any foals. Pinkie is their daughter, and wasn't lying when she said that her throwing her first party was how Equestria was made.

The first time Pinkie met Gilda they had hit it off with a tentative friendship, one side begrudging, rough and sarcastic, the other wary, hesitatingly cheerful, and secretly hopeful.
The first time Nightmare Moon had returned, the as of yet elements of harmony failed to get to Nightmare Moon in time to awaken the Harmonies and purify Princess Luna.

The first time Pinkamena Diane Pie made a Pinkie Promise, she changed her own name so she'd never forget it.

Pinkie'd never made good on her offer to tell the cutie mark crusaders how she got her cutie mark on their way home either.

And she'd certainly never heard of those things Zecora called Parasprites that drove Ponyville into a prolonged famine.