Natural optima occur in the middle
Akin's eighth law of spacecraft design says
In nature, the optimum is almost always in the middle somewhere. Distrust assertions that the optimum is at an extreme point.
When I first read this I immediately thought of several examples where theory said that an optima was at an extreme, but experience said otherwise.
Linear programming (LP) says the opposite of Akin's law. The optimal point for a linear objective function subject to linear constraints is always at an extreme point. The constraints form a many-sided shape-you could think of it something like a diamond-and the optimal point will always be at one of the corners.
Nature is not linear, though it is often approximately linear over some useful range. One way to read Akin's law is to say that even when something is approximately linear in the middle, there's enough non-linearity at the extremes to pull the optimal points back from the edges. Or said another way, when you have an optimal value at an extreme point, there may be some unrealistic aspect of your model that pushed the optimal point out to the boundary.
Related post: Data calls the model's bluff