Sony has used UDF for their Playstation DVDs and you can look at the files on the disc but you still can't copy them onto a DVD-R and play it as they use protections that can't be duplicated on a DVD-R. Just because you can see the content of the disc doesn't make it immediately possible to pirate them. For the Wii and GameCube discs only certain DVD drives along with special software could allow you to copy the discs but you still can't play them without a modchip or software loader. Playstation 3 games used standard Blu-Rays but you still couldn't copy them and play the BD-R without extra hardware or software on the system. All PlayStation 3 files on the BD-ROM were encrypted and you needed the PS3 to decrypt the contents.lol its a custom format its not any known open source format..., its like saying wiiu disc are simple blurays, they arent they would never use a known open format or else piracy would have been a thing on day 1 on wiiu games.
Just because you can copy the disc doesn't make it playable out of the box. Even if Nintendo used UDF or another open format for their games, you still wouldn't be able to play them without extra hardware or software. They wouldn't be that stupid.