The Mystery behind Genetic Code

The genetic code of most of organism is same. I believe that nature doesn’t do anything for random. Then why is the genetic code the way it is? There has to be some purpose behind it. I mean why there are 3 stop codons (UAA, UAG, UGA) and just one start codon (AUG)?? Is nature more inclined towards limiting proteins than exploring new ones??

Furthermore, why are there 6 codons for Leucine while just 1 for trytophan? I guess it has something to do the functionality of amino acid. More the flexibility of amino acid, more the no. of codons encoding it. More the specific the amino acid, lesser the no. of codons encoding it.