Take the requirements for example. If they aren’t airtight, you’ll get into a wordsmithing scenario where the contractor claims they met the requirement and it becomes a game where the team with the best lawyer wins. Write the requirements too explicitly and contractors will push back saying “tell us what you want, not how we’re supposed to do it.”
A somewhat silly example is if you specify you want unit testing on all safety critical code paths a contractor may claim they define running a compiler as “unit testing”. A contracting officer may not be technically savvy enough to push back and when the subject matter experts try to leave negative contract comments (that get reviewed when awarding future contracts) they get scrubbed because its not worth the fight in the eyes of the contracting officer.
Unfortunately, just saying “do good work” just doesn’t...work