Because they just keep making life more difficult for websites that don't need SSL.
So now in addition to seeing a scary icon on the url bar with a scary message, my users are going to have to click past an interstitial banner just so they can visit a website and read silly travel stories. Chromium will try their best to convince them to leave, lest some nefarious agency on their home wifi substitute alternate silly travel stories that somehow cause them harm. In the 20 years the site has been live, I skeptical that this has happened often enough that we need to get Google involved.
It's frustrating.