The bottom line is, the motivation for private enterprise is private gain, not public good.

Often enough public good may be achieved, and there is a case for the argument that on balance it is the best way to achieve this. However it is evident that there are situations where the goal of achieving private gain is incompatible with public good.

Criminal enterprises are such situations - there are plenty of very profitable activities which are illegal because of the damage they do. The fact that they are profitable is not seen as a reason why they should be legal.

The kind of corrupt business activities mentioned above are just one variety of such criminal activity. The fact that the activities in question may be profitable or "necessary" in order to carry on the business involved is irrelevant. The same could be said of drug trafficking, white slavery or blackmail.