Q:

Why has extreme programming (XP) gone out of date in favor of Agile, Kanban etc?

I like XP (extreme programming), especially the part where there are 2 programmers at the same screen, since a problem's solution is often found more quickly if only you explain what you're doing and pair programming forces you to explain what you're doing.
Over the last 10 years or so, the XP style of working seems to have gone out of date in favor of the working methodologies: Agile and/or Kanban. Why? Since XP seems to me to be a very good way to work and is a lot about the programming whereas Agile and Kanban are more about processes.

A:

There's a lot of different styles, methods and mindsets related to the whole field development, and everything has it's own, shiny name.
Agile is just a mindset that moves away from the usual, static programming models (like waterfalls) - it's primary goal is to achieve more flexible development and (at the very end) better software and happy customers. Below agile, there are a lot of different models like Scrum, Kanban, XP. 
Especially Kanban doesn't come from software development originally, it originates in building cars (i remind Toyota introduced it for building cars and some software developers adopted and expanded it)
Pair programming, code reviews and such stuff are just tools - you can (and should) always do it during a project, regardless which method you use. It's just that this stuff is more native to agile than to static.
XP more or less introduced these things (or at least gave them a shiny name) and all the following stuff adopted them because it simply worked out good.

A:

In my view XP is a programming practices, Scrum and kanban are project management practices. They have a relation but do not replace each other. 
In our kanban project we use pair programming (mostly for complex sections and debugging), TDD, CI. So it is still used but management is pushing the project management side harder.

