I don’t think many symmetrical, regular forms exist in the organic world. The egg is symmetrical around one axis, sometimes two (think turtle eggs).
Aesthetically it is a very satisfying form. It is very robust. The lack of a weak spot protects what is within.
It has symbolic meaning for a whole range of cultures.
And it embodies a conundrum: to release that which it protects it has to break – it has to be destroyed in order to realise its potential.