Do you lie on the forms collecting your personal data? We all do. This is normal and widespread. Why? Because users don’t feel the reasons behind some data collection justify asking for this data.
Take date of birth as an example. Most of the time no one needs this date for the purpose stated:
If you need to establish if someone is an adult or aged more that 13 years old, just ask confirm if they are an adult or aged more that 13 years old.
It you fail to give true or justified reason for wanting user data, the data you collect maybe skewed. Some of it may be correct, you may analyze it and infer something from it, but you won’t know how much of it is just plain lies of mindful users.
If you care about GDPR you should also consider if you correctly execute Art 5.