For weaker leaners the system can make rich material from previous years available. Not all material because that would be imtimidating and worse than useless. Material tuned by teachers over years to what the learner is trying to express.
An example is markup for a missing article. The reference contains some hints for median learners who understand the basic ideas but are having some trouble applying in this particupal instance. It is too hard for a weak learner because they stopped learning years ago.
Rather than slapping the weaker learners with a grammar book the reference might contain links to last years material which contains references to the year before that ... Never much material at a time and at the learner's pace so not intimidating. A learner might reach back four years to be able to express what he wants to.