This might be useful in a country where the government censors certain topics.
The government would still know (if they were logging traffic) that you accessed the page. In this case, as it is publicly accessible, the encryption is fairly meaningless.
The HTTP request is also encrypted, so figuring out what page you accessed on a site with millions of pages isn't quite as easy as you make it sound...
I'm curious as to why wikimedia is even offering all their content over ssl in the first place.