These keys come from regions where game prices have been adjusted to make them more accessible for a low purchasing power market, you as a rich bitch buying them is an inconvenience for publishers that drives the implementation of regional locks and universal prices. Additionally keys obtained through these re-sellers can be disabled, and there is very little G2A or Kinguin is going to be able to do about it. To be honest I don't even get why it is even legal for publishers to then remove these keys, the entire corporate world can abuse global pricing differences, but video game consumers can't? Still, the point remains that they can.