What the problem?
Often, startup founders can be genuinely misguided in assessing the feasibility of an idea or the cost of development and production, the "bottle necks" in a project, and the choice of materials and technology. Even if you already have a working prototype on Arduino and a 3D printed case, it does not mean that you will be able to easily scale this idea or adequately estimate the costs.
Investors also need to have a clear idea of how feasible the startup idea is, how accessible the proposed technology is, what the actual stage of the project is, and how much money, resources and time it will take to launch production. The speed (and the possibility) of return on investment depends on this.