I've purchased plenty from people on the site, mostly unopened boxes, completed sets, or near completed sets. Listing what you are selling may be a better way to get active buyers to look at what you have to offer. I wouldn't get disheartened so quickly.
As with anything, buying for me is based on the item, the price, and what else I may want to do with the money. I may want the Mickey Mantle rookie, and you may be selling it, but that doesn't mean I am buying it tomorrow. Also, I may want the last 30 cards to complete my 87 Topps set, but rather than go through the hassle of spending a buck or two to get them, I may have other priorities at that moment. Some people may just be listing them in the want category as a way to track what they want, but that doesn't mean they are actively buying (example again would be the Mantle rookie). I see you are newer to the site, I am hoping you didn't think it was a site where you can easily cash out a bunch of cards you want to get rid of. Give it some time, work some deals and make some friends. The site is a fabulous place for hobbyists and collectors and the categories to track cards in my collection/wantlist/trade and sale lists are awesome!
Look forward to seeing some of what you have to offer!