Redundancy of the genetic code
Wobble pairing is just a phenomenon and not a hard and fast rule. There are some justifications for why it should exist and that is why it is still called a hypothesis. And this statement is not true:"the base on the third position of the codon and that on the anticodon need not be complementary". The anticodon residue corresponding to the third residue of codon can be a promiscuous base which can pair with two or many different bases.  The tRNA for Phenylalanine has an anticodon - GAA which can pair with both UUU and UUC but not UUA.

So the statement of wobble hypothesis is that the first base of the anticodon (often is a modified/atypical nucleobase) can show promiscuity of binding.