If you buy software keys such as videogames from unofficial channels, you are likely hurting the original software developer. Most software developers will beg that you pirate their software instead. You also risk losing the software later if your key was bought with a stolen credit card, and the software developer chooses to void your key.

Developers tell people to pirate their games instead of using G2A - PC Gamer

G2A confirms it sold 198 fake Factorio keys - Ars Technica