In reality, in a full scale WROL societal meltdown following the first few days of relative "shock and awe", during which public empathy, compassion and compliance will wane, fueled by confusion, lack of information and direction, fear and panic, the real S will HTF. Big cities, with their crowded urban centers are basically deserts, without modern technology to support them. As the realization that their cities can no longer support them, citizens will begin to move. Not unlike a herd of cattle. spooked by lightening, they will stampede to whatever rural ares they think will have the basics for life. Even the police and National Guard troops will not be able to hold back the millions, if they haven't already left for perceived safety with their families and loved ones. All that will remain will be lawless gangs, feeding on the bones of civilization and not realizing that they are trapped in a "deadzone".
Those of us that live in a more rural setting will slowly see increasing numbers of "refugees" (we are 15 miles from a city of 50,000). The first to arrive in small towns or villages may find shelter, but as the numbers swell and pose a threat to those in the countryside, violence is the only outcome. What about mankind's "good nature"? Wouldn't those that have something want to share with those who have lost everything? If there is any semblance of governmental order and authority still functioning, wouldn't they mandate giving aid to the hordes that have spread out into the countryside? Surely, food and supplies will be arriving soon, along with personnel to restore order. Nope.
Think of a hurricane Katrina, but occurring in every state in the nation simultaneously. No internet, no television, no radio, no electricity, no public utilities, no law enforcement, no way for an unprepared government to function or even offer any help for the helpless. So, back to "Why would you need to "bug out?.
You would need to go"someplace else" if you were in a city because cities will rapidly become deathtraps in the event of a nationwide SHTF event. You would eventually need to go "someplace else" if you lived in a small, rural town or village because you would be overrun by desperate or lawless groups escaping the cities, looking for supplies (remember, groceries would be emptied within hours or at most three days). Even if you lived on a rural farmstead far into the country, you would be forced out by the remnants of the looters, like locusts picking the landscape clean.
Stay or leave? In the city, leave as fast as you can ahead of the mobs. In the country, stay as long as you can until forced to flee. What then? Find the largest, strongest, best armed, most organized group (gang) you can and hope you have some skill of value to them. Get used to a less pleasant than medieval lifestyle.