I've been reading a lot of online articles and blogs about advantages of using [HTTPS](http://en.wikipedia.org/wiki/HTTP_Secure) (HTTP over SSL/TLS) and the performance issues involved in deploying a website over HTTPS. What I understood is that the performance overhead in using HTTP over SSL/TLS is because of the use Asymmetric Cryptography in the Protocol and this overhead is highly dependent on the factors like hardware, server software, typical session length, caching behaviors of clients etc. 

On the other hand, many of the recent articles like [this one](https://devcentral.f5.com/articles/dispelling-the-new-ssl-myth#.UoUEO3Cfib8) claim that because of improvements in capacity and performance of modern processors and their architectures, performance is no longer an issue while using HTTPS. Also, SSL certificates are no longer expensive as they used to be. 

So, my question is, why are we still relying on HTTP when instead we can use HTTPS without any performance overhead on website? Is there any drawback of shifting all the communication over HTTPS?