I see room for improvement and expansion in every art. As others innovate, any given art can be "left behind" by not adapting to changes in culture, environment, and common practice. Even worse, they can continue to rely on mistaken information (imagine if sports teams still thought it improved players if they didn't drink during practice). Sharing of information between groups makes this growth and development easier for all. My primary art traditionally has a weak ground game. It existed, so NGA was a step ahead of some arts in that area, but adding a few tweaks from Judo and BJJ (easy to do since the arts share principles) turns it into something useful. It's still not going to match BJJ or what used to be common in Judo, but it's better suited to the art's focus. And if others (from other arts) know what I'm doing, they can give feedback on what they see in it (good or bad) that can help feed my development.
To finish answering your question, though, I have to take the other side - the question you sort of asked: what's the risk in sharing that. For a high-profit marketing system, there's some risk. Here, I'm thinking of those systems that sell hard that they have that "special sauce" that nobody else has. Most of us don't do that, so there's no significant risk in sharing that information. There's quite literally nothing in what I teach that would begin to be analogous to the Colonel's blend of herbs and spices. You can already find every bit and piece somewhere else, though some of it has evolved or been refined differently. If there's something that nobody else (outside a specific art) has ever separately discovered and made part of a useful training system, it has to be either an extreme statistical anomaly (by now, with all the experimentation in fighting methods, it should have been discovered) or nobody else decided it was all that useful. Given that the latter is inherently more likely (statistical anomalies of that order being, by definition, extremely rare), I'd want to figure out why they didn't, and the best way to do that is to work with folks who are not invested in its value - people outside the art in question. It could be an anomaly. It could be something simple that makes it less useful in other systems than in mine (perhaps it only really works well when surrounded by other, specific principles and techniques), or it might be that I've missed something that would improve what I do and teach.
Long ago, it made sense to guard information about fighting styles. They were actually used for routine skirmishes between groups, and those skirmishes were rare enough that the other group wouldn't have a chance to figure out your special sauce. So if they could find out (by having someone spy out the information) what that special sauce was, they could train to defeat it and would have an advantage over your group. That doesn't really apply in any modern context I can perceive, except gang wars.
