They are fed up with these scams, like me. Posting cheap / free GOG keys found or won somewhere and then linking to the Steam page to get the reward on IG according to the Steam pricing is intentional scamming as it isn't a Steam key (right on page one of the giveaway section you can read "Welcome! Giveaways are raffles that users create by giving guaranteed Indiegala keys or steam games. Enjoy and good luck!" This is an absolutely clear statement!). Some people like GOG keys nevertheless, and be it to come up with the next giveaway, some like me don't. Yes, good question: What is wrong with people?
Not touching the key and leaving a negative feedback is ok, it's not a Steam key so it's perfecly legitimate.
Activating the key on GOG or on other sites and leaving a negative is NOT ok, it mean that you haveaccepted the giveaway so you need to give a positive.
BTW, if the game is the same calling it cheap / free will not do it, a whole lot of games gived away here are from giveaways from other sites or reused keys that where got here, they are still ok, using that argument would mean not accepting any game thatcome to a previous giveaway.
Time ago i won a key on an external site but i already got the game so i made a giveaway here.
After some time i entered a giveaway for the same game cause i had extra coins and won my key back.
Made another giveaway and after some time i won it back again so in the end i made 3 giveaways with the same key, after that i don't know what happened to her.
Oh, this is actually something that normally must not be done, the site prevent you to use 2 times the same key, if you try it it will not let you make the giveaway, you need to put something extra on the filed to bypass the limitation, like "Stem Key: aaaaa-aaaaa-aaaaa".