These tags will pop up as suggestions as you start typing part of the word. I think we could discourage their use by deleting them altogether. You would still be able to add them, but then it's a deliberate choice. Now the fact that they appear as suggestion indicates that it's OK to use them, while in many/most cases it isn't, think australia.
So I propose to delete them.
I may be misinterpreting. Other tags show the number of questions between brackets, like "(5 x)" next to them, and these don't. Quick survey says there are indeed some unique appearances, others seem to be there as synonyms. I'm not idiotic enough to check them all. As I understand it the synonyms will be automagically converted, so it's possible that the other ones are indeed used, albeit only once.