Do we know that those heavy duty trucks were formerly used to do things you need heavy duty trucks for? It seems more likely that 18% (or more!) of the usage was by people who think heavy duty trucks look cool and wanted to show off theirs.
That's the difficulty with the Light/Medium/Heavy Duty categories. It doesn't tell you a huge amount about what the vehicle is being used for but most of them heavy duty mean commercial or utility. There are a handful of popular models that tip into the Heavy duty class and those are usually 3/4 ton pickups. Not sure how popular those are in NYC though.
