Key reselling websites hurt indie developers like us. There are many ways to obtain our games and we STILL prefer piracy over people buying from those websites.
Illegaly obtained keys are a source of money for scammers and it could even affect you as the customer in some cases.
Some developers find themselves in a situation were a few thousand keys are bought with credit cards and get charged back from the wholesaler.
Those keys are now out in the wild and they can put the hours in getting Steam to remove them one by one, but the chargeback from the original purchase are often resulting in fees.