Surely the point of airline PJs is that the airline provides them, for free, on the plane so you don't have that one extra thing to stuff in your carry-on or worry about having to bring yourself?

If I were a GE and got sent PJs from NZ, why would I be any more likely to bring them rather than my own PJs? (Assuming I want to get changed into PJs when on night flights, which personally I've never bothered doing. Maybe I'm missing out.. )