Ni is tough for Ne doms because it requires an uncomfortable break from our normal way of seeing things. It will occasionally happen, but not nearly as often as most of these "omg I use every function equally every day lol" people seem to believe.
Personally, I suspect that, since most NPs pride themselves on abstract creativity, any cognitive perspective involving seeing new abstract perspectives strikes them as something they should obviously be able to do well, so it's kind of a blow to their ego to consider that there's such a perspective that they're not naturally inclined to see.
That's why half the xNxP n00bs who show up on the forum always think Ni is one of their top functions. They just don't understand well enough what Ni is to separate it from what they know as "creative abstraction"--that being, of course, Ne. They read some poorly written description of it and figure they're probably good at it just because it involves an unusual and abstract perspective, of which they usually [erroneously] consider themselves masters.
There's a reason most NPs, when asked to describe their own Ni use, just describe Ne. Ni is so alien that they don't even get the difference yet.