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 the

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.