It is very common. The foreman on a larger project drives a truck and uses it as an office. They need a truck for some activities so it can't be a car (often because the tools are in the back), but they are spend a significant amount of time in the truck doing paperwork. Large jobs will have mobile offices brought in for the job. Even if you are a small company (think pouring a sidewalk), you still need a place to fill out the paperwork so you can bill the customer.

I can see that 10 or more years ago but these days I'd think that would all be done on a laptop or tablet.