The data protection and privacy interests of end users are relevant to any assessment of potential negative effects of the observed practice of gatekeepers to collect and accumulate large amounts of data from end users. Ensuring an adequate level of transparency of profiling practices employed by gatekeepers, including, but not limited to, profiling within the meaning of Article 4, point (4), of Regulation (EU) 2016/679, facilitates contestability of core platform services. Transparency puts external pressure on gatekeepers not to make deep consumer profiling the industry standard, given that potential entrants or start-ups cannot access data to the same extent and depth, and at a similar scale. Enhanced transparency should allow other undertakings providing core platform services to differentiate themselves better through the use of superior privacy guarantees.