This incentive is simply not in the public interest. In a different context, the lack of knowledge defended by government attorneys as reasonable would often be an insult to the intelligence of any self respecting public official. The enlightened way to avoid constitutional litigation is to prevent the constitutional violations that give rise to litigation. This requires that public officials be highly aware of constitutional rights and that they know the limits of their lawful authority. Exposure to civil liability promotes that awareness and knowledge.
Qualified immunity militates against it.
It is not in the public interest to sacrifice the quality of constitutional freedoms in the name of protecting the government from civil liability.