I’m a firm believer in bugging in whenever possible. That doesn’t mean that I’m opposed to bugging out when the need arises, just that I think that most people would be better off staying at home, where they have more to work with. However, even if your primary survival plan is to bug in, you should always have a backup plan to bug out, should the need arise.
As part of that bug-out plan, you should have your bug-out bag packed and prepared. Even with it your chances of survival may be difficult. Without it, your chances of survival are much lower. Of course, it’s impossible to carry everything you need in a backpack so many people end up leaving behind some piece of equipment or other, like a tent.