Do you have address? Seems its a funny question! No, its not a funny question. There are people who doesn't have an address (sometimes people deliberately hide their address for some reasons) in the society. Address proof is a mandatory requirement to open a bank account, getting admission / joining to an institution / office, passport etc.
Which is the most important document in our life? It would be Property documents or Qualification Certificates or Insurance policies or Share Certificates or Marriage certificate or Fixed Deposit certificates etc. There will be many answers depending on person's state of mind or circumstances. Back to the middle of 20th century and earlier, people were least bothered their birth date because, there were no questionable use of it, except a few people like Govt. servants, Teachers, Defense personal etc. Others, majority of people, only aware that they are living in their locality moving here and there and doing some kind of job or business.