The difference is that Google had a clear unique value proposition that was to provide search results (and only search results) back extremely quickly and were highly relevant when they other players were focused on creating "web portals" and did not focus attention on search.

With CodeCombat and Codeacademy there UVP is very obvious (make learning to code a game and teach to code online resp.) and had not previously been done. With this site I don't understand what the UVP is (social programming challenges?) that hasn't been already by something like TopCoder, Sphere Online Judge, etc.

"Achieve mastery through challenge" is the tagline. The idea here is to push yourself to solve problems you may have not attempted before, and to learn from others by seeing how they solved theirs. I've have personally learned a lot from seeing how other people solve problems, I even learned a lot from creative uses of solving "Hello World" which was a bit of a surprise.

In short: Codecademy is meant for those who want to learn programming. Codewars is for existing programmers who want to get better at programming.