I'm a prepper but my main two motivators are severe storms and job loss. Being in a rural area power loss is common and during the last big hurricane this area had no power for 3.5 weeks.

Job loss. I got laid off in 2009 and thankfully we had an emergency fund and it wasn't much of an issue. I did stress about the whole ordeal though. If we have life's necessities stored up and no new job was to be had then we could survive for a good amount of time.

EMP. Now here is your fringe reason. I do think that the way to hit America and got it hard is to take our power away. This could be done from a ballistic missle overseas or even a container ship in the gulf of Mexico. If an emergency we're to go off then a large portion of the country would come to a grinding hault.