Yes, it’s quite an unusual situation. But sometimes you just have bitmaps to display, eg. how would you create a simple image viewer in JUCE? Or sometimes it’s much easier to rasterize an effect instead of somehow converting it to paths.
Knowing the DPI is not enough, you also have to know the exact offset where to draw the image so it lines up with the physical pixels. We currently work around that with g.setImageResamplingQuality(Graphics::lowResamplingQuality).