Why would they do that? When Nintendo has like millions of unsold Wii U's sitting in a warehouse and are not manufacturing anymore.
They need to figure out a way to sell their old stock of Wii U before NX comes out.
It's only in Nintendo's best interest for the Wii U to be fully hacked, so they can sell more hardware.
It's not like Nintendo is racking in the dough on royalty fees from third party devs, since they have no third party support. They need to sell more Wii U's, not more software to 20 people who own Wii Us.
Piracy is a good thing for Nintendo at this junction in their console's life.