I wonder if this is significantly influenced by the images you find when doing an image search for "<search term> transparent". A lot of sketchy clip-art sites

I wonder if this is significantly influenced by the images you find when doing an image search for "<search term> transparent". A lot of sketchy clip-art sites insert the checkered background, probably to both symbolize transparency and also to prevent people from just right-clicking "Save as...". You want the user to search the download button on a page full of ads and fake buttons after all...