Why do transfer agents require complete data sets?

As per current requirements, all shareholders must have a correct name, address, country of residence, and tax ID if they are a US/CDN investor. Completeness of data ensures that your records and data are compliant with current SEC, IRA, and OFAC guidelines. 

If your company intends to go public and get listed on a stock exchange, your company will also require complete shareholder information to comply with relevant SEC and stock exchange listing requirements. This may include a clean legal opinion and audit of your existing capitalization structure. 

Please visit links here and here for more information on SEC requirements on datasets.