Dictionaries are boring.
They are just pages and pages of words - few people sit down to actually read a dictionary. We use the dictionary as a metacognitive tool - it is part of a strategy for problem solving. The dictionary only jumps to mind when there is a problem. These are, of course, the basic problems encountered by students when using the pedagogical dictionary. Much more linguistic information is contained in the learners' dictionary than in the normal monolingual dictionary, or even the pocket bilingual dictionary.