Please don't be maliciously facetious.
Because the design IS what we're looking at. We are looking at the art and science of designing a website to effectively deliver a webcomic. I don't care if the comic updates, or looks bad, or has bad writing. It just has to be designed to deliver a comic. The information is relevant to you regardless of the featured comics update schedule or quality. So long as it effectively (or ineffectively) achieves its purpose.
We might as well review sites that are not even comic related.
Those reviews WOULDN'T be relevant, now would they?