This is one time where we need to step back and look at the NEC as a whole.
Sure, it might seem silly to limit the receptacle spacing rule to only residential locations, but keep in mind that there are many instances where the NEC makes this distinction.
In residences you can have any number of receptacles on a circuit; everywhere else load calculations kick in. Most circuits are sized according to their loads - but not the residential 'convenience outlet' circuits.
In residences you are not allowed to have 277v. lighting; everywhere else you can.
It is assumed that commercial occupancies will have a better level of planning, and that the maintenance crew will be better trained. Homes, by contrast, are seen as 'one size fits all.'