Or to catch modules that have somehow reset to factory defaults! (...ahem SwitchLinc...)
Personally, I leave A1 and P16 clear so that I can do testing of a newly installed device before assigning it a permanent address. (P16 is the factory default for PCS)
The keychain RF remotes that I have are units 1-2 on a selectable house code, so one would need to keep that in mind when assigning addresses (I think some are 1-4 too).
But I see no reason to avoid entire house codes.