Why is it necessary to provide personal information during registration?

The personal data serves to classify you for the surveys relevant for you. Often, surveys only pertain to a particular group of people, e.g. women, because a man generally has little interest in women's handbags. The address data is only used for the positive identification of your person, i.e. that it is really you who is participating in the survey and not some "alias" you have created. This is for security purposes only and also guarantees the correct payment of the remuneration for your participation.