Having all ads in one place is tremendously useful. Whatever one is searching for, it takes time to locate a source first, one that would gather that exact type of ads. There is no guarantee that those sources are complete and contain all ads that have been posted by users. Usually, viewers have to browse through a multitude of such websites to find what they are interested in. 
Ads Rage is the ads directory that helps people find all relevant advertisements in all categories from their city or area within the US territory. Go to http://usa.adsrage.com/ to find the precise ads you are looking for.