Adding SSL to a site sounds easy but it's very difficult in some instances. Take for example a forum, we can force everyone on HTTPS quite easily but as soon a

Adding SSL to a site sounds easy but it's very difficult in some instances. Take for example a forum, we can force everyone on HTTPS quite easily but as soon as someone hotlinks an image in a post that's not HTTPS it'll throw security warnings up which are (in my opinion) overly dramatic and are very unfriendly to the user experience. User submitted content and HTTPS can be a pain to get right, and on some platforms like common bb software it's basically so time consuming to modify it's just not worth doing. SO solves this by using imgur as a proxy, a lot of sites don't have that luxury unfortunately or even the technical expertise to implement something similar. This is also a bit wobbly on the old copyright laws as well.