Re: Housekeeping pads
If you were to install a panel in a location where the work area in front of the panel did not provide for safe operation, you could be required by NEC 110.26 or 110.32 to provide a pad or some modification to make the area safe. This is one reason Utility companies typically require pads at service switchboards that extend out enough to provide for safe operation, this could also be applied to a panel you have installed on the exterior of a building where the ground is uneven or rocky etc. Under most conditions, as pointed out by Roger, pads are not required by the NEC.