Dispatchers tend to dislike the extra work associated with running a special.
Especially one with an increased potential for breakdowns, or other problems. Steam excursions bring with it the increased likelyhood of nuisance lawsuits, and other potential liability concerns. Much as I would like to see a LOT more steam, today's social and business climate isn't exactly hospitable to it. Dispatchers tend to dislike the extra work associated with running a special. Especially one with an increased potential for breakdowns, or other problems.