I will never do it ofc, my personal documents are my privacy and I should not let others to use it for any purpose including to undergo KYC in gambling sites.
Even if someone is willing to pay me to give my personal document, I will always think twice due to the possible risks that my give me something really bad in the future.
However, it is common thing happen in my country where people are willing to give their personal documents such as ID card to be used by others because of small amount of money.
I have no idea why they did it, whether they do not care about the risks or they are not that educated about the risks so they do it.