Dropping to below 12 credits (the minimum for “full time” status) has financial aid implications. If he has 15 credits but is considering dropping a 4 credit course, this can be a big concern.
Merit scholarships may require a college GPA minimum to renew, so low grades may result in the college becoming unaffordable due to loss of the merit scholarships. Or even not-so-low grades like B grades if the renewal GPA is 3.5 or something like that.