I definitely see that too especially in jobs for homeowners where people might not know better to add time based penalties into contract. But you also see this in city work from city employees using city equipment where there is none of this contractor gamesmanship going on, only an ever increasing backlog of work from aging infrastructure and a municipal government disinterested in facing the music and paying for the associated increases in labor demand.

Even with all the availability of equipment and labor on hand, sometimes you must wait for the excavator to do its job first before you can begin. You cannot weld a pipe together when there is still earth to clear and the pipe to be welded is sitting on the truck. You cannot parallelize all work, some is inherently serial.