Transparent Slide Backgrounds in PowerPoint when "Saving as" Images

I have the background of all slides set to 100% transparency, yet when I "Save as" to PNG images, the slide image backgrounds are white. I can save each slide as a picture and get a transparent background, but that is way to much work. Guidance. Would love an explanation of why when the user explicitly marks a background as transparent you would export it with color. More MSFT customer focus...