I'm a PM in construction, and you will always see this with government contracts. It's actually the smarter option financially if you're running the show, which is absolutely bullshit.

The reason is that these companies will directly bill their hours for labor to the government. Since the government doesn't really have a way to verify any of this, it's better to have more laborers on site, even if they aren't working, to get more overall hours and thus more pay. It's how the construction companies squeeze out extra money beyond the initial contract. For some reason, in my experience, this is a lot easier with the government, since everything moves so slowly with them and needs to pass through several "layers" of approval before any action is taken.

With private contracts it's a lot less likely, because the clients usually have stricter budgets in which construction companies need to out-bid each other (with lower contracts) to gain the job. Most extras are back-charged and thus unprofitable for the construction company.

I've seen government contractors go over-schedule for months on even basic bridge repair work.