Maybe they get laid off, maybe the company moves and they don't want to move with it... but for one reason or another, they're in the worst position possible. They have no job, and they have allowed their IT skills to deteriorate to the point where they are no longer employable.
If you're in IT, you must be constantly learning. You must continually take the long view, and ask yourself three important questions. First, where do you want to be in three years? Second, what are you doing now in order to reach this goal? And finally, if you were laid off today, are your current skills sharp enough to quickly get another job?
That third question can be the hardest of all to answer honestly. I'm reminded of Microsoft announcing years ago that they would no longer be recognizing the MSCE 4.0 certification, since the network operating systems that certification was based upon would no longer be supported by MS. (Keep in mind that this change was announced months in advance, giving those holding the MCSE 4.0 plenty of time to earn the latest MS certification.)
Some MCSE 4.0s just went nuts. Microsoft's certification magazine printed letter after letter from angry MCSEs saying that their company would always run NT 4.0, and that there was no reason for them to ever upgrade their certification.
This wasn't just denial. This was career suicide. Let's say that their network never moved from NT 4.0. Let's also say that they got laid off yesterday. Would you want to go out into the current IT workplace and have your most recent network operating system experience be on NT 4.0 ? I sure wouldn't.
The fact is that you've got to continue studying, continue growing, and continue learning new things if you want to have a successful long-term IT career. If you plan on studying only one topic, getting into IT, and then never cracking a book again, you're entering the wrong field. And for those of us who have been in it for a while - again, ask yourself this question: "Am I prepared for what would happen if I were laid off today?" And if you're not, do something about it!