MAM credits you with points that can be used to buy upload credit or to make downloading a given torrent not count against your total bytes downloaded (freeleech)

Torrentleech has a point system as well and also automatically makes torrents above a certain size freeleech.

For both, the accumulation of points is so generous that you'll really only run into ratio issues if you go looking for them. Hell, MAM has so many people that are perpetually sitting with the maximum amount of points available and fantastic ratios that they have lotteries where users with more points than they could ever spend can spend them gambling on upload credit, but with the ability to spend more on a ticket to increase the prize (but not increase the odds of them winning). The practical upshot of this is that users who don't increase the prize get a much higher expected value for an entry than users that do, and those users i talked about that have more points than they can spend essentially use those points to buy other users download credits.

You're absolutely right that the base torrenting system is one where someone has to upload every byte that's downloaded and vice versa but these trackers are designed to ensure that basically anyone who makes a good