Because the modern web is based entirely around invading the privacy of every user as much as possible in order to sell their private details to advertisers. If

Because the modern web is based entirely around invading the privacy of every user as much as possible in order to sell their private details to advertisers. If Twitter's money came from users in the form of subscriptions or purchases, rather than from advertisers in the form of paid, targeted ads, this would be guarded information, rather than shared.