Just because they are labeled “low search volume” does not mean they will not be displayed if there ever is a search for the keyword in question.
It sounds as though you are focusing on long-tail keywords. Long-tail keywords will have fewer searches, however, if you add enough of them to a campaign they will collectively amount to a significant number.
I would suggest that keep those keywords and look for more keywords. If you use the AdWords Keyword Tool and set the match type to “exact” you will see the actual search volume history for each keyword idea. If you study the terms that are frequently used by searchers for your niche you should be able to cobble together hundreds and even thousands of long-tail keywords.
All it takes is a handful of impressions for each keyword, multiplied by thousands of keywords, to reach a significant number of impressions.