I think because NT8 uses complied Net DLL files thus, making it more difficult to see the source codes. Top of that, it also uses Agile, making it harder to compile and to do a reverse engineering on it, especially when it is obfuscated.
Then comes the encryption of key data along with external servers for key validation.
But then, who am I to say.ð
Regardless though, I do see people selling "cracked" versions of NT8.
So, it certainly can be done and achieved.