You get to use both ends : including the one to remove boy scouts from horses' hooves, and I only get to use the pointy end!
The thing I said about "messing about", goes double. If the butt-end was truly important there wouldn't be a plethora of funky styles.
My experience includes some background in aikiken and aikijo from several different lineages -- mind you, I'm not claiming exhaustive mastery of those usages, just enough experience to recognize a few commonalities -- as well as sword and polearms in two distinct koryu. Additionally, I've been fortunate enough to observe a number of public and private presentations of other koryu in which I don't actively train. I have certainly experienced wide variations of training methods and goals within aiki-buki practice, and even broader variations across multiple koryu. In the former case, these differences are associated with individual instructors working off a somewhat common base of material. In the latter case, the differences are associated with a much broader range of factors -- historical era in which the school arose, social class of practitioners then and now, geographic location of practitioners, and primary focus of the school, to name but a few.
Some older schools are dedicated exclusively to the practice of one weapon, others address usage of multiple weapons while retaining a primary orientation toward one of those weapons. Some koryu schools (or lineages within larger groupings) retain a combative sensibility, others are more in the nature of cultural preservation societies. All of this makes generalization rather difficult.
But that said, I can assure you from personal experience that a polearm in the right hands is not a mullet -- business in front and party in the rear -- and that entering into an engagement with the assumption that it is such leaves one quite literally open to some exceedingly ugly possibilities.
Perhaps you should consider the possibility that, as many direct students of the Founder have repeatedly told -- and continue to tell -- their students, aikijo and aikiken are not intended as strictly combative systems, but rather, are intended to provide a medium for teaching a range of principles, not least of them reinforcing the basic patterns of body movement taught in this or that group or aikidoka.
As the late Sugano Sensei once said in response to a query about why he didn't emphasize sword (or more broadly, "weapons") as a part of his instruction, "if you want mochi, go to the mochi maker."
This seems to me a much sounder proposition than making assumptions and pronouncements regarding the nature of polearm combatives on the basis of experience with a system of movement with sticks which has been designed to emphasize -- according to its disseminators -- something other than a strictly combative purpose.
Of course, we all have a natural tendency to relate anything new that we encounter to something we already know, in which regard your observations about the lack of efficacy of the butt end of the stick may be accurate -- based solely on your prior experience.
Forgive me if I've belabored the point, but it is also my experience that the tendency of many aikido practitioners toward unwarranted assumptions that one's experience in aikido provides a sound guide to judgment regarding the principles underlying older combative systems, or the expression of those principles in particular patterns of movement or other elements of technical application, has resulted in a noticeable reluctance on the part of a number of licensed koryu instructors to accept students with a background in aikido. This seems to me an unfortunate, but understandable, situation; whatever your own personal training goals, please give a moment's thought to the possibility that ill-considered statements such as yours might not only be merely wrong, but may themselves cause difficulties to other aikido practitioners with rather less unwarranted certainty about the scope of their own knowledge and rather more curiosity about approaches to budo and bujutsu that predate the development of aikido as a gendai budo.