Which reports require the activation of Advertising Features?
Cohort Analysis reports
Demographics and Interests reports
To make the Demographics and Interests data available in Analytics, you need to update Analytics to support Advertising Reporting Features and enable the Demographics and Interests reports. When you enable Advertising Reporting Features, you allow Analytics to collect additional information from the DoubleClick cookie (web activity) and from Device Advertising IDs (app activity).
Read more here: https://support.google.com/analytics/answer/2819948