I think that's exactly the problem: the assumption that philosophers should assume, by default, that self-help is unworthy of their time, and only pay attention to the rare cases that happen to have philosophical merit.
They could take a more active interest to questions such as, how can philosophy improve self-help literature? What kinds of ideas should ordinary people with low to average education consume? The wide array of values, goals, and philosophical approaches would make it a contentious and lively conversation.
But philosophers tend to vacate the field and leave it to mercenaries, culture warriors, and amateurs. When they do speak about it, it tends to be in symposiums or on podcasts aimed at college-educated people with a special interest in philosophy. That's as far down as they're willing to dumb it.