Out of the box lattice structures are not always suitable for all industries. For example in the medical industry, designers wish for the capability to create their own lattice structures because certain structures promote better bone growth for patients. The ability to define your own lattice structure is key for certain design tasks. In the upcoming January 22nd release of NX, you now have the ability to create and store your very own lattice structure.
See here for a demonstration from @Paul_Bevan on this exciting new functionality.