Why No Keyword Filters!!!

Why has Google Adsense not allowed filtering by keyword yet??? I have been a fan of Adsense and have used it for quite some time now, but, I feel it is still flawed without keyword filtering. As a premium publisher I know for a fact that you can filter this way, because I have done it. But, as a basic publisher like 99% of us are, there is no option for this.

What bothers me the most about it is the fact that is truly is useful. I have been working on my CharlotteGarageSales site for sometime now, and I am running ads down the left side. I feel ads can be very important to a site if done correctly. Now, my ads would convert at a much higher rate if they displayed Charlotte based content on stuff pertaining to the area, not stuff of garage sales. Look at it this way, if you were hunting around and found a nice site on garage sales in your city, and was actually browsing the sale listings, would you click on an advertising link that said "garage sales" or click on the link that maybe said "charlotte restaurants" or "charlotte jobs"?

I rest my case, conversion and ad relevance is going to be based on good filtering, something we just have not seen yet!!! Lets hope this entry is completely irrelevant tomorrow!