There are many times that I haven't deleted a plugin through the WP plugins manager because I get the warning that it will also delete the data, and I think that I want to keep the data as I might re-install that particular plugin later. There are also times when I've had to reinstall plugins due to a corruption, and again I don't want to delete the data, so I have to revert to FTP to delete the files. Conversely, there have also been many times when I look at a database and groan at how much junk there is there.

So, like most things in life, the decision really should be mine. When I click delete in the WP plugins manager I should be given the choice to delete data. In fact, it would be nice if there were 3 options: Delete Files Only; Delete Files & Data; Delete Data Only.

This should be a mandated part of the core WP plugins system which all plugins in the WP repository that have their own tables have to implement.