Scrum and XP

My guess: Marketing. XP is marketed toward developers and many of its practices are highly developer-centric. Scrum, on the other hand, is more of a project or product management framework and the concepts are graspable by the business people who make decisions about how to run efforts. Even though Agile methods are all about self-organization and self-management, getting buy-in is necessary to be successful.

That said, I'm sure many organizations using Scrum in the context of software development are using Extreme Programming practices. Pair programming, TDD, continuous integration (and continuous delivery - XP's CI is inclusive of what many people consider to be CD today), and collective code ownership are all closely associated with XP. Other practices, like maintaining coding standards, simple and evolutionary design practices, developing a system metaphor, and working at a sustainable pace are also XP practices but seen in many Agile Software Development methods and frameworks. Even though an organization may not be fully practicing XP, they are likely taking advantage of practices developed in the context of XP.

at least in name

There you go. Fake programming is perhaps harder to spin by a management bubble, and by definition could only ever appeal to a very restricted IT market.

but just 1% using XP!:

Some organizations are using "Scrum" as a primary agile framework as it is defines simple roles & ceremonies in a sprint based approach and gradually trying to integrate some good XP practices side by side with Scrum like Pair Programming, TDD, System Metaphor, CI Collective Code Ownership etc. 

So, We can say that they are using hybrid framework by mixing other practices based on their need and empirical experience. 

...Scrum seems to have become (at least in name). The State of Agile survey found 66% using Scrum but just 1% using XP.

I believe that you answered you own question with that snippet. There are a large number of companies that say they are following Scrum because they use some of the Scrum terms. So when they see the questions on the survey, they respond with "we are a Scrum shop".  I would not be surprised if the actual number of organizations that have implemented the Scrum framework as described in the Scrum Guide are in the low teens. 

As for using XP I have not worked at any company that did not use some of XP's practices.  For example, User Stories came from XP and they are somewhat of a standard practice in those "Scrum" shops as well as in most implementations of Kanban.  Paired programming is used almost everywhere at various times.  The Daily Standup is referred to much more often than the Daily Scrum.  The standup is an XP practice. 

I don't put much faith in those surveys because they ask people to select from a list.  Most people don't fully understand the implementation details behind terms used to describe agile practices.  In fact most people feel that Agile is an actual methodology and not some marketing term adopted by companies trying to capitalize on the the intention of the manifesto for agile software development.