Not having a LinkedIn account would be definitely a red flag for many companies. However you have the control to display as much information as you're comfortable with on your profile.
Why? I have had same thought as op. Even as an address buck of loose employee connections it feels pretty useless. A lot of people I might want to ask for a recommendation or advice on a role, I would probably reach out over Facebook or email since it feels more sincere and so much is lost in the recruitment noise on linkedin, especially for software people.
Haven't had a linkedin profile like OP for a long time. Never had any issues finding a job or getting interviews. Stackoverflow careers CV page is my resume and the contacts that come through Stackoverflow are consistently of high quality.