The signature signifies human personality code that tells the world how an individual would like to be viewed, particularly at this age of computers and word processors, the signature remains one of the evidences of a personal identity that a human being can be identified with.  For instance, take a signed document, the signature on it is you, who signed it. So you are your signature,  it is accepted as such on official documents,  namely: driving license, credit cards, passport, personal ID, library ticket, medical card, National Insurance Card,...