Yeah - 'cos whoever heard of a private entity being corrupt?
Look - while the independent agencies are funded by the various governments, the funds ultimately come from taxes paid by (among others) the people of the country. Ultimately it's those people those agencies are answerable to, because they are chartered to ensure their safety. Imperfect as it is, I for one have more faith in that social compact than I would in a for-profit organisation trying to do the same.