Say the company you are contracting for has a strict policy on things like account sharing and giving out of passwords.
Then say that you are being explicitly told to violate this policy by your manager at this company. That manager is a full time employee of the company whose policy you are violating. Management at the compnay you work directly for are aware of this, as well, and are complicit. They expect that you will go along.
What do you do? Do you stop and throw a fuss? Do you just go along with it? What if you are concerned that making an issue of it could cost you your job, both at the company you are contracting for and at the company that directly employs you?