Often, the best designs are so simple, elegant, and practical that we say "I could have done that!". That, of course, is not true or we would have done so.
Often, a new object or a new design is the result of a process which begins from the recognition of a problem. A good designer will then work to solve that problem in the most elegant way possible. If they succeed, we instantly recognize how good the solution is and, often more importantly, the problem for which the solution is the answer.
As an example, I ran across this someplace on the web (BoingBoing, I think):
I find this to be an elegant solution to a problem I had never considered. But seeing the solution has prompted me to be more aware of difficulties that the sight-impaired encounter. No lightbulbs have flashed yet but I have a deeper appreciation for the design.
By keeping the faces all white with only the Braille dots as differentiators, the designer has turned the problem on its head for us. He is showing an example of a game that is as hard for us in full light as the colored version is for a blind person. But the design is not just a polemic, it actually solves the problem for the blind.
Here's the BoingBoing
link. Some of the comments are interesting, too.