“Today, Facebook does not use your WhatsApp account information to improve your Facebook product experiences or provide you more relevant Facebook ad experiences on Facebook. This is a result of discussions with the Irish Data Protection Commission and other Data Protection Authorities in Europe. We're always working on new ways to improve how you experience WhatsApp and the other Facebook Company Products you use. Should we choose to share such data with the Facebook Companies for this purpose in the future, we will only do so when we reach an understanding with the Irish Data Protection Commission on a future mechanism to enable such use. We'll keep you updated on new experiences we offer and our information practices.” [0]
WhatsApp may not show ads, but Facebook is paid for by ads, the data collecting in WhatsApp is so Facebook can show ads elsewhere.