We had a discussion on this about a year ago in our Feedback subforum. As our technical guru, Tom Westbrook, pointed out at the time, an SSL certificate would be a recurring cost for us, and as a non-commercial site we are running on donated resources and time and have no regular income stream. I'll add that it would be another item for Tom to deal with. We may get to it at some point, but we cannot promise whether or when.
In any case it is not good practice to use the same password across different websites.