well im just fussy lol
imagine you were washing mud, tar and debris off your hands and you just put soap on them, rubbed it in and then wipe them dry with a towel and didnt use any water. it wouldnt work as well would it? and thats exactly the same as what your doing here except your paintjob in most cases is far more fragile and prone to damage from grit than the palms of your hands.
theres no denying it will work and shift the dirt, but it will leave your paint job with swirl marks without a doubht. and you just dont want that on a sexy skyline with an expensive flipcoat paintjob... or even on your micra for that matter 
carnauba wax is the business i must agree with you there though
