Language proficiency maintenance
It may be a realistic language learning goal for a competent speaker of a second language to maintain their existing level rather than language proficiency improvement. If a second language learner neglects studying their L2 they are likely to regress through second language attrition. They may not however have the time or motivation to commit to language proficiency improvement. They may even be aiming to pass an exam for which they're already good enough to get the top grade, and want to devote energy elsewhere. In these circumstances the aim may become to avoid regression.
Most courses however assume improvement.