Earlier quoted context omitted.
Nope this is directly linked to ad revenues because StackOverflow don't care about them they can offer freedom. And if they ever get into financial difficulty you can count on me to subscribe to a paying "gold membership" and I still won't care if broken students get the same content for free and without login. You never wondered why there is very few fake account on stackoverflow as compared to ad based social netwo…
Why would you think StackOverflow doesn't care about ad revenue? They both run ads and want to make money by helping recruiters reach logged in users.
Registering non participating members is only a trick to inflate your user base when communicating. What really matter is active users, and they will register don't worry.