Perhaps they are, but when you are looking for an older game such as the example above and you have to pay 3 times as much to get it from the official retailer then it's up to the individual on what to do. Also, another thing to mention, is that I haven't had any problems with Steam or Uplay or Origin with these keys, either getting banned or not working.
I will always make sure it came from a source that supports the developer. If not, there aren't any funds to make games. Because it works, doesn't make it ok in my mind. I myself, will not support gray market resellers.
Don't feed the Trolls