> Like piracy? It's ilegal and fines are often hefty so shouldn't it deter people from pirating movies or downloading roms etc?

Yes, and it mostly works! Bans on piracy work well already, most people don't torrent games or movies. And locked down platforms exist, demonstrating the technical feasibility of even greater control. Software piracy in particular is much more difficult on the sort of computers that manufactures deliberately design to be locked down, like modern video game consoles and iOS devices. It is still possible, but has been made sufficiently difficult to stop the majority of the population from doing it.