Investors, developers, and shrewd business people designed the most popular method - those who understand the concept of divide and conquer - it is when contractors get little or no down payment for a construction project, do all the work, including change orders, and then try to collect their money.
What often happens is that contractors hate paperwork preferring to keep everything in their heads. Then when it comes time to collect their money, they have to re-sell the job and talk their customer into parting with their money.