Chris Lopez, the communications head of the Denver host committee, and in my video, says that:
union restrictions and the needs of people planning events might be limiting who gets convention work. For example, printers used by the DNCC must be union shops and there's only a handful of such businesses in Colorado.
The Rockymountainnews reports that print shops must be union, but there are scant few in Colorado, so those that aren't don't get work.
Well, time for Colorado to "union-up."