Ehhh, the 'collect it to use internally' is a bit inaccurate. While not literally saying 'here buyer is user data that we are offering to sell you' Facebook, Google, and every other platform do sell user-derived data to advertisers in the form of native audiences or other targeting products. 'Oh you want to to serve ads to individuals that shop at Uniqlo? Here's a list of profiles to target that have checked into a Uniqlo three times in the past 6 weeks'. 'New-Parents? here are inds that have dwelled on babies-r-us (I have no idea if they still exist) or clicked to learn more about a stroller ad that was served in their Instagram feed'.

It's not 'here's all the activity data about Anthony Mouse', and user data is collected internally, but it is also baked into targeting products that they sell to brands and agencies.