part of it's also shitty contracts that don't match reality.

They don't ask for a finished price, they ask how much for X M³ of dirt removed from here, Y M³ of concrete here.

When those amounts don't match up, the price of the project changes.

The overall number is what wins and loses the contract, so if you can identify what's going to be an overrun, and what's going to be am underrun, you can low-ball and highball numbers, come in the cheapest on the bid and then make plenty of money.

If they wanted to stop that, they could get better civil engineers to write the proposals or stop line itemization (at the cost of having to negotiate change orders)