You have an incredibly complex process that is very hard to sequence and dozens upon dozens, like I said, of different types of labourers working for different companies who all have to show up on site. Anyone who's in the development industry knows the difficulties associated when one sub-trade doesn't show up for a day—they're a day late or they're behind on another job—and the ripple effects this has.
This translates as well to your previous question about municipal inspections and the role of the building code. If there's a delay in a building code inspector arriving on site, your site's effectively shut down until they arrive. That's not a particular knock against any individual inspector—they work very hard—but there is absolutely a need to standardize these processes in a way that we can have certainty on the quality of product we need to build to the highest standards and there aren't the slowdowns that are associated with that sequencing issue.