Linkedin - Does it Work For You or Does it Have a Negative ROT - (Return on Time)?

I have a Linkedin account like almost everyone else who works in financial services but I am not sure it adds any value to my career. I have 600 connections, who are mostly former colleagues and clients. Over the past 10 years or so, I have had many inquiries for services but only one person has actually taken the next step and made a financial commitment. I get linkedin requests on a daily basis from people who I may or may not know. Sometimes, these people don't even work in the same industry as me but they still want to connect with me. So far, I have viewed these requests as potential business opportunities . I will accept the connection and send the person a message asking if they need help with an exam. Most of the time, the person says no. From linkedin, I have literally have earned like $200 over the past 10 years. My ROT has to be incredibility low, haha

I realize there are ancillary benefits to having a Linkedin account such as the account giving you some credibility and it serves as a way to keep connected with people. I am just not sure if accepting linkedin requests makes much sense for me, as it wastes a lot of time. I can see how Linkedin would benefit someone who is at the beginning or his or her career, though.

Does Linkedin work for you and if it does, how to you benefit from having an account?