It depends on who you are and who you are trying to reach. If you are a for-profit business or institutional "person" then you only really need to reach people who are the type that give you money or who you provide services too. That means blocking people due to HTTPS CA or cert issues is okay. If you're a human person or government then you want the information or service to be available to as many people as possible and that means HTTP+HTTPS even if it means allowing older versions of HTTPS.
Because HTTPS is harder. The user could be loading HTTP content from another host on their page. In order to support this you would basically need to modify their page (including scripts) to rewrite all URLs to HTTPS. This is nearly impossible to do perfectly. I think they are right to give their customers this option if desired.