Issue trackers are mixed blessings. We deliberately chose not to work out of one at my current workplace for various reasons. Instead, if we encounter a bug or a user reports one, we deal with it on the spot or we add a task for it in Scrumy, which we use with weekly sprints. If something's not high priority enough to go in there, we just drop it instead of amassing a backlog that's kept out of sight. It's not a problem if we forget about a low priority bug since it's probably not worth fixing if we're not often reminded of its presence by reencountering. Of course, this doesn't work equally well for all teams and products. But I wouldn't call an issue tracker an absolute no-brainer.