My reasons for needing a fast mobilization:
(denotes my experiences)

1) Nuclear Industrial Accident, Nuclear ICBM Attack; Nuclear Terrorist Attack:
(1962 Cuban Missile crisis, Duck & Cover Drills @ elementary school)

2) Hurricanes:
(Hurricanes: Betsy, Camille, Andrew, Lilly, Katrina, Rita)

3) Tornadoes:
(During hurricanes)

4) Highway Accident involving Hazardous or Explosive Materials:
(Too many to keep track of when living next to an Interstate Highway)

5) Railroad Accident involving Hazardous or Explosive Materials:
(Hazmat: May2008/Lafayette, La Explosive: Feb1968/Laurel, Ms)

6) Civil Unrest/Martial Law:
(Limited Martial Law/Feb1968/Laurel, Ms)

There are many more reasons to be ready for a fast mobilization, IMHHO (In My Honest Humble Opinion)