QF may well consider them single use only, but passengers don't. How often do you see discarded PJs in the cabin? And if they were single use only, why bother putting a logo on them?
That's my point - why should I parade QF (or any other airline) logos in my own bedroom? I prefer to buy my own PJs that fit perfectly, do not shrink after washing and do not advertise airlines

My favourite PJs? Sleeping nude...