If a product is free most likely you are the product. I don't know how exactly but I don't believe Musk is doing it just because of his big hearth.
He is doing for his tesla I guess because in future driverless cars are going to have more consumers so if he can provide lot of free perks then people will get attracted to his car and of course he can track the user data and can make use of their database for his future product engagements.