Social connections, networks that enable employment, and a lack of serious financial reserves (which will always be true for ~50% of people) are the main reasons.
And no area is immune to disaster and lacks challenges.
The "low natural disaster" areas have a total lack of warning before disaster strikes, heavy snowfall that can cripple normal services, deserts with poisonous creatures, or some combination of those three.
For the most part, to be perfectly honest, as long as you are capable of picking up and moving on short notice...hurricane country is actually safer due to the amount of warning you get.