I'd much rather have short, low revenue trains in the winter powered by diesels and the D&S earn money or break even during those months. That also extends the amount of time between rebuilds and inspections of the steam fleets boilers.
Given the announced plan to return all three K-28's to service in a rotation with the K-36's, I don't think the D&S plans to retire it's steam fleet. 18 months for a complete rebuild might stress the existing fleet. The loco's are getting up there in age and things happen. Better to create windows of opportunity to do maintenance and reduce wear and tear when possible, extending the operating life of the fleet.
I'd rather see the trains be powered by steam during the busy season and diesels provide power when the passenger count is low in the winter.
We can complain about the "almighty dollar" all we want. If there aren't enough dollars, there won't be any trains running. It's just the way it is.
Besides, it's not like the diesels owned by the D&S aren't interesting in their own right. The Rio Grande certainly had no qualms about using them when provided a pair by the U.S. Army.