The issue is most developers do not bother to write any, and the ones that are written are most-often vapid typing failures ("these`int`s cannot be negative" should be handled by a type). I studied this field in grad school, and the entire problem almost always devolves into convincing developers to engage with the system.
I find that is the case with almost all methodologies for software quality improvement. If you can't enforce that people follow it then it's not worth anything.
