Why should I provide so much information when creating my user profile?

To create a user, only a username (first name, nickname, etc.) is required. All other information (name, social security number, date of birth, sex, height, weight, medications, chronic illnesses, allergies, blood type, and medical information) is optional and is only used to collect your medical information for you in one place. This is especially useful for the export function. You can find more about this here.