What is the deal with the "stop stealing" on the gallery?

The bottom line is that this is a respect thing. Creators put in all the effort and creativity into making these builds and they feel proud of their work. Proud enough for them to put them on the gallery for everyone to see. Most creators don't mind if they're being downloaded and used for their personal gaming experience. It's when those people who make minor changes and reupload someone else's work as their own that changes things. Some creators don't mind it but have the respect and courtesy to credit and acknowledge the original creator. Whether or not you can see the original creator, the person who reuploads it should do it themselves.