I guess it all depends on how far and where you are headed. If I've got to "bug out" without a vehicle, I won't be looking to take a big heavy pack to slow me down.

The bigger issue is where would folks bug out to? If it's like rats fleeing the sinking ship, most will end up drowning. If they are hoping to stay with a relative, what if nobody's home when you get there (or worse). It's hard to plan for disaster - too many unknowns.