Why video gets skipped
Video is a second production pipeline: another brief, another shoot day, another edit, and a per-SKU cost that only makes sense for hero products. So most of the catalogue never gets any.
Generating from the image you already have changes which products can justify it.
Sized for where it runs
Every channel and placement wants different dimensions. Assets export to any dimension with border fill or generative fill, so one source produces the aspect ratios each placement needs rather than a crop that loses the product.
Ad visuals and banners follow the same route, which keeps a campaign visually consistent across placements.
Related
See also aspect ratio, generative fill, ad banners and videos, or read how Photogenix fits the rest of the workflow.