For the edit, my guess is that you are from USA, in which case we have to clarify, I guess also that with government agents you mean police forces and "assimilated", e.g. FBI, when operating in the USA territory, in which case, can be easy to see why they want to avoid the complications that would derive otherwise - honestly, some may present it as ethics, is more probably a practical matter to avoid public backlash, plus, imagine someone gets a confession while pretending to be a priest and tries to use it, it would be a feast for the lawyers.
If you mean any kind of government agent from USA and operating no matter what, that is a different matter.
Actually, that type of figures are in many cases the best ones to go collect and spread information.