Starting in May 2018, the Uber app will no longer support connecting your phone's contacts to your account. This optional feature allowed the Uber app to make personalized recommendations for you (such as suggesting which friends to invite). The contacts from your phone will no longer sync to Uber servers, and previously synced contact information will be deleted.
The app will continue to ask for the contacts permission if you use features that display your address book within the app, for example: Trusted Contacts, Split Fares, Share ETA, Invite a Friend. Uber will continue to store the information of specific contacts that you select when you use those features, such as the friends you split fares with.