I doubt that it would be that easy to get others documents. Sure if you are in Colombia or something and people are starving, offering a few dollars to them would make their life easier and that would be a lot better for them, it’s really easy to understand what it would look like.
But, if we are talking about something that is dangerously risky for the people who do it, like literally getting caught levels? Then it would put them in danger and people who are doing that type of illegal stuff wouldn't want to be in there. Even giving others documents would cause them to get caught if that person speaks, and you may feel at ease for 1000 of them not, but one of them could eventually and that’s a risk.
If you know this business you would easily know that people from the third world countries jump into this KYC documents selling for few dollars only and forging the document is another way of fulfilling KYC requirements.So getting documents is hard directly from person but they go through these different ways to obtain the documents and should be avoided at any cost because it has many problems if you get caught.
People in third world countries don't understand the importance of KYC. It is true that they can sell their documents for few dollars. They just fell that they have nothing to lose, there is no problem if their KYC documents are stolen. But with the change of era advance technology is used everywhere. when it comes to KYC many platforms ask for their live video of a few seconds so identifying real person is very easy at the moment.