To be more accurate, mobile apps delegated the 'login' to a primary login service, such as your phone number, email, facebook account, device ids and so on. N

To be more accurate, mobile apps delegated the 'login' to a primary login service, such as your phone number, email, facebook account, device ids and so on. Nobody wants to remember 50 logins for the 50 apps they've downloaded just to try them out.