Mostly for advertising purposes (apparently). A more complete picture they can build the more advertiser's will pay.
That said, I wouldn't be surprised if FB was a front for NSA to collect the world's data. Give it forty years and something like this will come to light.
Shhhhh, let's blame the poor for all our problems and forget about the Panama papers which literally showed billions of pounds being harboured by UK citizens away from our tax authorities.
Please stop telling people how they should act to enjoy music. Maybe the kid is loving it but enjoys music by standing still? People can do what they f***ing want, that's the beauty of art.