A duress pin is useful if the cost of the government getting mad at you because you wiped your data is less than the cost of letting the government have your data. Whether that holds depends on your situation—for example, whether your phone's data could implicate other people that you want to protect

When talking about costs we should remember who is paying. Maybe overall the cost of the government getting that data is higher than the cost of them getting mad at you, but when a single individual is paying for all of it the equation might change.

I think it's a matter of personal privacy. You shouldn't show it to other people.