The OP does not mention what country they are talking about. It seems to be more common in the US than in many other countries to forget to mention that. So we

The OP does not mention what country they are talking about. It seems to be more common in the US than in many other countries to forget to mention that. So we could guess which country the question refers to. Legal things are always national. What could be common practice in country A might be void or illegal in country B. Doing a Web search for my country results in plenty of hits. A recurring focus seems to be agile development. That requires of course special consideration if the contents of the work has not been defined to great detail when signing the contract.