I disagree that the reason most people take up aikido is that they are interested in it as a spiritual path. They may COME to see that but based on my experience (14 years is a moderate timeframe) most people come in, see aikidoka practicing, seeing people being thrown more or less effortlessly around and are mostly interested in wanting to be able to DO THAT. They may be interested in it as a self defense art, or as a physical activity, but rarely have I ever talked to a new student who walked in and had them say "my I want to use aikido to develop myself spiritually". Just ain't so. Of course they didn't realize we are at least most of the time cooperating with each other, and only after a protracted time of practice can we "really" take balance and "really" effect the throw. If they hang around long enough to get there, then they may have started seeing the "spirituality" of it all.
I agree with you Don that a few people join an Aikido class because they want to emulate the seniors they see in action when they come to check training out. You must agree though that most don't come to check Aikido by chance, most of them have read articles, websites, books about it. Most people will check different martial arts ethos and philosophies BEFORE checking them out visually. There is no doubt that a large majority of beginners is aware of the fact that by joining Aikido they have the chance to get something more than flicking people around, if, as you said they stick around for long enough. My point was that too often the commitment needed is nowhere to be seen, while the typical Aikido-we-are-so-so-special-talk is ALWAYS there....