If it were an org that wasn't likely to have its own I.T. department or a website that is hosted by a webhost that wasn't in the LE list, then I would definitely do that. But one of the sites I did this for recently was one connected to a Canadian public school district and the other was for the freaking New York State Department of Education. I should hope they have I.T. departments in those orgs and that staff knows about MITM, etc.
I'm also in the middle of composing a letter to someone whose site is hosted by Squarespace and I'll use a similar template for this use case scenario as well, except in that I'll be adding the link to the "Source" page. That template looks like this:
Dear WEBSITE OWNER,
I hope all is well with you today. I found your website while doing THIS THING AND I THOUGHT YOUR SITE WAS USEFUL, ETC.
At the same time, I noticed that YOURWEBSITE.com doesn't have a security certificate (aka "cert") as in the attached image. YOURHOST offers free certs for all their website customers and here's a link to the Support page that tells you how to do it: LINK TO PAGE LISTED IN THE LE THREAD LABELED SOURCE.
Thanks again!
Again, this is low-pressure and something that other folks in this community who want to encourage more SSL use can do without needing to vet articles. In fact, just looking at the Squarespace article it's even written in an excellent way because it talks about the benefits in ways that are tailored to their customer base's use case scenarios.