The difference is that theft is a criminal offense, where you’ll be prosecuted by the state.
Violation of a software license is not a criminal offense but a breach of contract, opening you up to civil suits. So, it’s up to the rights holder to file suit and drag you to court for damages.
Both break the civil law , you can absolutely sue the thief for damages for lost property.
Typically this is not done because it is not worth the lawyer expenses as recovery chances are pretty slim unless it is a kleptomaniac billionaire maybe , instead you claim insurance to recover on your losses.
Similarly copyright theft is also same as any other property theft, you can charge under criminal law as well , typically success rate is not high , but people have gone to prison over pirating movies or bootlegging stuff etc
So what’s the case law for violations of the GPL? Did anyone get criminally convicted prosecuted for violating any software license at all, and was anyone convicted? I’m only aware of civil suits in this regard.
