One major sticking point for schematic diagrams is the format. Schematics can be drawn in many ways, but component symbol libraries quickly become an issue.

One distinction between general-purpose graphic editing software and schematic capture packages is that the latter are supported by component symbol libraries. These allow you to specify a component by name and have a recognizable symbol appear on the drawing surface. Without that feature, drawing schematics would quickly become a tedious quagmire of decisions, first about how to present a given symbol approproiately for a given application, and secondly how to store it so that it becomes a symbol rather than a collection of lines and shapes.

Someone would have to make a decision about how to accomplish that before schematics could conveniently be reated, stored, retrieved, etc. Additionally, there's the question of existing formats, specifically, how to convert from them to the "universal" format used in the target forum. That, certainly, would be a task I'd prefer to leave to someone else.

PDF is a possible format, but tools with which to generate PDF from the very many commonly used formats are not yet abundant.

RE