I guess it's because those sites have content that are largely public anyway. That is, you don't have to login to consume their content. They still would redirect to https when you do sensitive things like logging in or changing your profile. Content driven sites don't need to face any problems with SSL. Even major CDNs have https URLs nowadays. I don't see any reason at all not to use SSL for a web application today. It's just that a lot of sites started before SSL became commonplace and they haven't moved to encrypt the whole site yet. I believe Jeff Atwood (stackoverflow.com's founder) would have made stackoverflow.com https by default if he started it today. You can read his thoughts on this matter here - http://blog.codinghorror.com/should-all-web-traffic-be-encrypted/ Just checked .. Quora does redirect to https by default.

Yes it will. It is additional computing effort and naturally it will use more resources. But it's only a very tiny fraction of the total request processing time. You won't lose the benefits of caching. Server side caching is all about how you have designed your application. Browsers cache content even if they are delivered through https. I haven't developed 'high-traffic' applications in their general sense. But in the applications that I have developed so far, I could not observe any difference at all in performance or user experience. Also, if my application does suffer any performance loss because of SSL, security would still be my priority over performance.

I'm thinking the same about Sublime Text 3. I still miss the smoothness/speed of Sublime Text but Atom's growing steadily to be my new favorite.