Not if they are contractors. That's the point the parent commenter was making. All the reasons you list make it so they need to do so, instead of "hiring" them directly.

There are definitely gray areas to the law, but in my decades of experience dealing with lawyers, they won't steer you to do something very far over the line. I think the companies that do step far over the line, to game the system, are doing so knowing full well they are breaking the law, but they believe they are unlikely to be caught. And they're very likely right. You could separate CEO's/CFO's in to two camps: stay legal and do what you need to do to make the almighty $$. In the 80's the phrase "greed is good" was born, but the last 2 decades have really upped the ante on this.