If it is a hot opportunity, you will want to be able to move in ahead of the competition, and not lose time sitting down and typing something up. It doesn't matter how good of a worker you are, or how loyal you think your employer will be to you. Stuff happens, and sometimes it's not good. You realize that when you get up in the morning now, you're not looking forward to going to work anymore. Your job is boring, you know your supervisor's job better than they do, your pay is going nowhere, and the future doesn't look very bright.
Rumors are in the air about an acquisition, merger, or layoff.
Your boss says not to worry, but you get the impression that she started to do a lot of discreet job-hunting recently. Your spouse mentions, for the second time, what a great career opportunity it would be if they could accept that new position at an office in another state. The additional advantage of frequent updates to your resume is that it will help you record your accomplishments. That great job you did on the last audit, and the praise you received from the divisional VP because of it, may just slip your mind in a few years - so add it to your resume now. One other absolutely essential point - the function of a resume is not to get you a job.