I have the same problem. Torrents/trackers from other sites will continue to seed after I've completed my download and give me good ratios. I tend to think there is just a different type of user for this site and for some reason the demand is not that high. Which is very odd as, of the four sites I visit for torrents, this one has by far the largest offering.
Or the site owners have found a way to get people to donate to get their ratios up and not lose access by managing traffic…but that's just a conspiracy theory. Doubt that would happen.