Most of the candidates that I reached out to for many of my openings are not active job seekers. If I have done the correct research, my hope is that I am presenting them with an opportunity that is a great match for their background.
Candidates should, at least, be willing to speak with the recruiter to learn more about the company, the specifics of the role, and also the compensation package. Many times, the best opportunities come up when you are not actively looking to make a job move. Also, you are in a much better negotiating position as someone who is actively employed versus someone who is losing their job or has already lost their job.
I have seen too many cases where candidates "pass" on an opportunity because they are "comfortable" in their current job. Unfortunately, some of the same candidates reach out to me months or even years later in a panic because their job is being eliminated because of downsizing or financial instability.
It never hurts to explore a job opportunity presented to you. Worse case scenario is that you spend some time exploring the opportunity to find out that the role is not a match. Best case scenario is that the unsolicited call presents you with a wonderful opportunity to enhance your career. Time very well spent if this is the case!