With static webpages, the concern isn't someone snooping in on what I'm reading. It's someone injecting content, probably malware, into the page. Let's say I have a zero-click exploit for Chrome. What can I do with it? If I just stick it on a page I control, best I can hope for is spamming it all over the web and hoping someone clicks on it. Probably not a lot of impact before it gets patched. If instead, I can wait until some router firmware gets pwned, or an ISP, I can do a mass attack where I make all the vulnerable routers inject my exploit into all non-HTTPS web requests. Much greater exposure.
