Meta keywords are not used in search rankings, and usually sites use these in a very uncontrolled manner. It is usually better to use a more precise and controlled set of topics if they exist.
Note that lower level fields may sometimes be needed to compute more useful fields. Also, sometimes the higher level fields may be more difficult to compute, so they are not always worth it.
Since the value in general is low, this is not imported by default. That said, you can scrape this out.