LinkedIn is huge. There is simply no other way to say it. People are connected and have access to an infinite number of resources. So while people can certainly decide for themselves how and if they use LinkedIn, it should be noted that people who do not, make themselves (in my opinion) look a little out of touch professionally. I recently scheduled a lunch meeting with a candidate. He asked me how he would know who I was when he arrived. I suggested he look me up on LinkedIn, which has my photo.
He thought that was a good idea.
I thought that was obvious.