Everybody's got a party and if you leave, you ruin the party -- apparently. Isolated "walled gardens" are a kind of Intranet. Ingress requires buy-in (sign up, log in, identity proof, human proof); leaving means breaking out to the more transparent, connected internet, which is a big problem when data is dollars.

Maybe I'm reading too much into it. More and more patterns seem hostile, antagonistic to the user, and it seems like it's an adopted practice that's taken as a standard. I hope I'm wrong.