Because you got better service by paying then getting pirated copy and have nothing else then that? For same reason why people pay Minecraft, you would get pirated version that let you play only on few servers or pay for it and get access to all servers including most famous once? Same goes blizzard old games people have tendency to pirate and then buy game just for CD-Key because thats how good multiplayer was. Note that all of this is based locked service that you need to pay for, thats why everything switches to *-as-service model, because thats more efficient way to deal with piracy without imposing scary DRM. That would not apply to blueprint code which doesn’t have service to back it up and can be copied with clipboard and even send via chat.