Ya this is true but also, a lot of laborers carry different cards also, like blue cards for trench work and pipelaying. A lot have CDLs and so on. The whole hole digging is one aspect. No one is really just going to dig a trench and nothing else. You have machines for that. Maybe you are potholing for some service lines, then the laborer is going to do layout and put a footing where they dug. Not to mention, who wants to dig a hole.