More often than not, losing your job comes as a complete surprise. In my experience, when people get news of their termination or a contract ending early, they find themselves in an uncomfortable position - hit with a sense of urgency to find something new.
In this situation, people typically apply to every job they come across and send their résumé to every firm they can find. If a firm happens to have a job that seems like a fit, they will likely reach out to the person and start the process. However, if they do not have an open position at that particular time, they probably will not contact the candidate. If they don’t know the person and don’t have a high likelihood of placing them soon, they will see no need to take the time to have a conversation.
However, if you have a relationship with a recruiter - meaning that you keep in touch periodically - then there’s a higher likelihood of that person more actively helping you out. In this case, even if the recruiter doesn’t currently have an open position, they will still take the time to call you back and, more often than not, make a few phone calls on your behalf to see if they can find you something new.
Most recruiters spend the bulk of their day on the phone, talking to candidates and clients within a specific industry. It’s their job to keep up on trends within that industry, what companies are growing/hiring, who may be downsizing, etc. It would surprise me that such a person wouldn’t want to have a periodic five-minute conversation with a candidate whom they know and like. Taking a few minutes of your time, a few times a year, could pay off when you find yourself, unexpectedly, in need of some career help.