Because practitioners safety, avoiding to develop competitive feelings amongst the members of the team, avoiding focusing in techniques and tactics that only make sense in sparring, maintaining the status quo, aiming to a specific demographic market niche etc. can be seen as more important than the benefits obtained if serious sparring was included as a pedagogical tool.
There has been a lot of work done and money spent to create a specific image in the minds of the people of what aikido is about, what is aikido for, how aikido should be trained/taught and how aikido is politically structured.
Serious sparring in aikido can be as dangerous and counterproductive for this "building" stability as making IS/IP training available to the masses and the cannon fodder.
IMO, of course.
So spot on it's scary. This is again why I hate political things!
Looking away from Aikido as a money making venture, you would agree that sparring is a total necessity? At least in the sense of learning to "use" Aikido as a martial art.