This varies by jurisdiction, but perhaps I oversimplified. There is another reason that doesn't happen.

The individual engineer doing the work needs a license, but the company itself also needs a permit to practice. The permit must be held by an engineer, who is personally responsible for the engineering that occurs under their permit.

So, the permit holder needs to worry not just about their own ethical behaviour, but that of all engineers in the company. They are incentivized to ensure the company will hold the public safety paramount, or to walk away if they cannot (thereby leaving the company without a permit).

If the company has a pattern of misbehaviour, it may be difficult to obtain a permit.