consider this scenario: developer is tasked to make an update to a report. He does not have reporting services available locally (long and complicated setup) and neither does he have access to the data he will be reporting on (because of data privacy regulations). He makes the change to the report, checks in the code without any testing and it then blows up in qa. This is a common scenario that i have seen many times before, especially when developing for systems or with data that developers don't have full access to.