Breaths are sticky. Once they are put in an object, they stay there forever. Stormlight, on the other hand, has been described as “wanting to flow.” In the same sense that you (presumably) can’t change Stormlight into Breaths, a Larkin probably would not be able to steal Breaths from people. Even if it could, Larkin consume Stormlight. They have likely evolved to do so, and may have some trouble consuming other types of Investitiure.