I don't understand why the market for keys still exists. Only allow direct purchase. I brought two games last year through steam and ubisoft which I was later

I don't understand why the market for keys still exists. Only allow direct purchase. I brought two games last year through steam and ubisoft which I was later given a ban for because I was in a range of stolen codes. This affected me as a legitimate user buying direct. Game code reselling needs to end.