I don't live in hurricane country, so I don't know, but how many folks go to a hotel/motel when they evacuate? Especially folks with kids, and with a busy hurricane season that could cause multiple evacuation warnings, that's a signficiant expense. And we're assuming car travel. Many folks may need air travel to get away (think of the mass exodus from Japan, particularly Tokyo, of mostly foreigners high tailing it out of the country due to radiation fears).

Let's not forget the psychological aspects of evacuating for many situations. There is a powerful need for folks to stay and "defend the homestead," especially if the disaster is not guaranteed to be deadly. Even with wildfires here in California, so many people who had ample lead time will not leave their homes until the flames are bearing down on their homes, even the ones who aren't actively fighting the fires. They have the car packed up and the keys in the ignition but they just need to wait until they absolutely have to leave.

I have also encountered the "cut'n run" desparaging attitude that some folks have regarding getting out of Dodge. Different culture, but to a large extent, that's basically why essentially only the foreigners were fleeing Tokyo, not the Japanese. It's a negative kind of peer pressure to abandoning their neighbors, friends, or fellow citizens.

Finally, there's also the "boy who cried wolf" aspect to repeatedly bugging out, which is going to happen when the practice is get-out-early-get-out-every-time. The vast majority of people tire of that very quickly and become even more resistant to bugging out in the future than if they had never done it the first time. Bugging out is often a hassle and an inconveniece even in the best of times so people don't want to do it, especially if you have children involved.

Just thinking about California where landslides and wildfires are typical reasons for needing to bug out. Just need to go a short distance to be safe and not usually for long, but even then, a lot of people don't want to.

The decision to stay or leave is not only--maybe not even primarily--a logical, rational choice for a great many people IMHO. Any arguments for or against early, speedy bugging out needs to take the psychological aspect into account, in addition to greater population-level limits and hazards to such a policy that ki4buc pointed out earlier.