There's no reason to limit it. If you have a cap on traffic, it's better to monitor the volume of traffic cut it off when you are close to the traffic limit. Because the ratio on each torrent correlates only loosely with how much traffic each ends up consuming.

This is especially true on private trackers because you want your ratio to be as high as possible. Especially if you are downloading rare torrents, it might be hard to have enough leeches to even get to 1.0 ratio. So you can make up for that by also downloading more common torrents and allowing them to seed into the 1000.0s.