Image optimization sometimes doesn't seem to be working?

Image optimization seems to be working only for a subset of images on my projects homepage. Is there any criteria that would cause an image not to be converted to webp for example?

Hey Jay! Image optimization should work for any non-SVG image that has been uploaded to Plasmic (i.e. except pasted URLs).

upon further inspection it appears the images that were not being optimised were set up as background images is that the expected behaviour?

Sorry - indeed background images are also not optimized.