When it comes to digital preservation (such as in a digital repository), where chances are that the archive maintaining the files may not have the original software used to create them, using a well-documented, neutral, stardardized format (such as PDF, STEP, or IGES) is preferred over proprietary file formats that do not get much use outside their native community. Granted, my motives are very different than those in the PCB field, which is perhaps the cause of the confusion. Right now, I am dealing with a collection of PCB files and Gerber files (which we are trying to convert as well.) My main objective is to transform them into a format that can be read by most regular users who have basic computer packages (Microsoft Office, Adobe Reader, etc), or at most a CAD program that can read neutral formats like STEP and IGES. This is done for both longevity reasons (formats that can be read by free and multiple programs will generally last longer) as well as access reasons. Also, converting to standard formats that can be read by many programs is done simply because we do not have the budget to purchase all the software programs we'd need to maintain the files in their native format.
I hope this clarifies a little bit more as to why I'm asking this question.