Totally situational. What if you are travelling anyway or just out shopping across town when the SHTF? Being more than just a couple of miles away from home could be life threatening. Having a mobile stash of essentials could save your life.
Mobile stash is not your entire hoseold prep considering moving to another location permanently.
Exactly why I have a bug back pack in my car...inflatable and life jackets as well as water to cross water...seems silly but I am happy to have it and supplies are there to bug in!
Pets depend on me too...although dog is likely to be with me. I have his pack and life jacket too.
Thanks to this thread I realized if the causeway was closed I needed both a bug out and a bug back bag. Hope I never need the bug out ones!