We could easily be ready to go in half an hour. I have yet to find a compelling reason to be more "prepped" than that.
Fire.
In the city, we have the possibility for things like chemical spills, civil unrest, gas leaks, bomb threats that may be cause for evacuation. You do not need to worry about most of those things, but fire could be a compelling reason to prepare yourself for a possible bug-out scenario. It is up to you whether you feel 30 minutes is enough time to evacuate your home in case your surrounding property (or your home itself) is on fire.