Regardless, since you had come to Equestria, you had yet to do what should have been done and ride one of the residents of this world as you were so accustomed to in your own. Most ponies, Changelings included, were simply too small to handle the stress of your weight, and those that were large enough were royalty that would find it unbecoming to let you do... but apparently totally fine with you delivering a hot load of human spunk whenever you damn felt like it. 