Another thought here is what hard work is involved with the solo training offered by Dan (and others) and how long it may well take to achieve a level of proficiency that provides useful results, results without thinking. Many will not take the time and will drop the practice if they don't see results the following week or so. Some will see the level effort needed to even get started and be underwhelmed..... It is easier to be underwhelmed than do the time.
Adding on to that thought --
1. When feeling this stuff for the first time, even the first few times, it doesn't register in our brains what we are feeling and where it’s coming from. We look for something familiar to connect it to, and that familiar something usually is physical strength. Some of the underwhelmed are those who just write off what they are feeling as being conventional muscle power and body mass/weight, particularly if the person demonstrating is large and muscular. We are conditioned to equate size with physical power. Of course, that notion is quickly dispelled once smaller, slighter practitioners start demonstrating on the big guys. But if there aren't any present, some individuals may come away less than impressed because they couldn't discern the skills as separate from the physical size and appearance of the individual.
2. Some folks attending a seminar geared toward beginners and newcomers, mistakenly think that the introductory seminar curriculum represents all there is to the method. Furthermore, attending just one or even a few IP seminars, without really doing the work after and in between is not enough to inculcate skills or fully appreciate their value. It takes a couple years of serious effort to start seeing the real effects and to understand what one is doing with his or her body. To be able to apply the skills and maintain the body state under duress takes even longer. Therefore, people who attend one or a couple of IP seminars and then state that they don’t see any benefits, simply don’t have the level of skill and understanding yet and are writing off the training’s value prematurely. As with any discipline, we must be motivated to truly do the work in order to gain the benefits.
3. If the presenter doesn't perform Amazing Feats to awe the crowd, those who come expecting a magic show will be... underwhelmed. Even more so if the teacher parses out the material into bite-sized pieces of information and basic exercises that demystify the subject and the process and lay out the path to development, step-by-step. For a few this may make it seem ordinary and unimpressive, particularly if they get caught up in the component pieces, mistake training exercises for the skills themselves, and fail to see the big picture. For the rest, the vast majority of us, though, the wonder of IP and aiki become even greater once the mystique is dispelled and we begin to understand how it works.