As a dancer, I think that ballerinas have beautiful feet. However, to a non-dancer, all that is seen is a distorted and unnatural-looking foot. Non-dancers don’t realize that ballet requires pure self-disciple, and part of that is disciplining your feet to do unnatural things.
When I see a professional ballerina’s feet, I see the hours of exercises and the years of constant practice that has gone into sculpting that perfect arch. Non-dancers don’t generally understand the amount of work, diligence, physical and mental strength required to achieve the perfect look.
If you want a technical answer, it is because we use basically whatever we can get our hands on to stretch and pull and push our feet into beautiful arches (walls, sofas, thera-bands, etc.). We consistently exercise specific muscles in the foot (metatarsals, tarsals etc.) and dance on our toes with the support of pointe shoes (sometimes known as toe shoes). Feet are as important to ballerinas as hands are to gymnasts and are used as frequently, which means that our feet are also very calloused and muscular.