The reason is simple why not to allow automatic requests: The coordinators may have a certain IP allocation scheme in there minds. Maybe regional, maybe some other criteria. That means that not every request out of the blue fits that scheme. So an IP range may be unallocated, but it does not fit the allocation scheme. An coordinator would change the requested one allocate the right one, which would not happen in an automated system.
e.g. in YO, I allocate IP ranges based on regions, so that the first number in the block fits the requestors region number (the same as in the callsign). I had requests like "please allocate 44.182.35.xx to me", the user being in region 8. It resulted in allocating the first unused 44.182.8x.xx /24 subnet to him, and not the original requested one. This would not have been possible in an automated system.
Marius, YO2LOJ