The question is what if the fire is by your door so you can't grab your Buff and go down the stairs. A bob could be helpful in an earthquake as people have been known to survive a few days under a pile of rubble until rescue workers dug them out, if your bob is always within reach it will be under that pile in the "cave" your in with you making you able to survive it easier.
I actually don't have a BOB myself in the normal sense of a bob. I have all my shelter in place gear organized and stored in different rooms and in different containers/bags/boxes that make it all portable. If I do need to bug out then I grab whatever is near me and go and my shelter in place gear becomes my bug out gear.