Salt
Salt adds taste and strengthens the dough. Without salt, your prata will taste very flat and lifeless.
Egg
The egg proteins help to strengthen the gluten and makes the flipping easier. The egg white helps make the dough more resilient and the yolk contains lecithin which helps emulsify the oil. The egg also adds more nutritional value to the dough. When I omit the egg, I find my prata tears easier when I am flipping it.