ISPs or anyone could still insert malicious javascript into your site, or present download buttons or login features on your site.

Visits to your site could be logged by IT departments, getting your users in trouble.

Also I've actually heard of places where port 80 is actually blocked by default (but 443 isn't) and you need permission on a site by site basis to get it unblocked.

because if security and privacy is only limited to sensitive or controversial sites, then the use of security and privacy become suspect. If ALL internet traffic were encrypted, it would make surveillance that much more difficult because you can't find the signal in the noise. Cory Doctorow's book, Little Brother, talks a bit about this... in fact, that book was one of the motivations for Google starting to encrypt web search traffic years ago.

(more of my own writing on the topic: https://willnorris.com/tag/https)

I, as a potential target for Mitm, would like to be sure that what I'm accessing is your blog, and not some phishing crap.

Presumably your lolcat blog still has an admin login, and in the spirit of the first part of the article, even this would be HTTPS'd.