Tjin makes a good point; the purpose of a BOB (bag) is to be useful in bugging out on foot. If you can't cover ground quickly carrying all the gear you need and "might" find useful, you have a largish survival kit in backpack form, not a BOB.

The concept of a BOB (my primary intent is to bug in) that I prefer, is that it be no heavier than what you'd use as a GHB. I have lots of supplies at home, no need to carry more, so I carry just what I need for a walk home and possibly an overnight along the way. That's it.

As I envision it, a lightweight BOB allows you to move from point A (where you're bugging out from) to point B (a well stocked destination). No need to carry extraneous gear, just carry what you need. You may need to be able to move like an ultra-light hiker.

All that said, when I do need to bug out, (as I've said many times) I use a truck.