different materials have different properties... about losing pleats when washed:

Poly COTTON kilt will lose their pleats after each washing and must be re-ironed. Acrylic kilts keep them pretty well. Poly Viscose keeps them pretty well also. Do you HAVE to iron a PV kilt when it comes out of the washer and dries? No. Should you to "neaten it up a bit"? Probably.

The reason you don't have to iron your wool kilts... do you wet wash them or dry clean them? if you WET wash your kilts (hand wash with woolite and lay flat to dry) like I occasionally do, you WILL need to iron those pleats back in.

I hate ironing and started sewing down the edges of the pleats on our casual kilts so I never had to iron them if I didn't want to... that's what he's referring to. Hope that helps to clarify!