Actually they aren't "legitimate reasons", they're personal preferences.
flots.
I have no issues whatsoever with octo inflators provided the diver understands them and get's familiar with them. When I sued one, I put longer corrugated and LP hoses on my rig so it was quite easy to use. To keep the set up from dangling the reg/inflator stored loosely behind my console (see above).
I personally use a necklaced alternate, but for blue water recreational diving, the octo inflators are fine IMO.
They are quite common here and I personally know of a number of OOG rescues that were effected with them without issue.
I have installed an Atomic SS1 on my daughters rig. She breaths off it regularly and we practice with it. I also have her primary 2nd on 40" hose under her right arm with a 90 degree at the 2nd.
I have seen too many traditional octos "get lost" and prefer she know where it is at all times. And she does, as she handles it often during the dive.