If someone clicks the Keyword difficulty in their account, and then a completely different person on another account find that keyword later, would he have to look it up again?
It will display the KD but if you want a fresh KD then you can click it and update it :)

Most other tools using KD saves it in a database, but gives the option to update it as it might have been a long time since it's been updated.
Yes we are aware and working to display more data. But at the moment this is the way we are doing it. We hope to have a very large KD database in the near future