Don't need them, again they will not stop the collar curling under slightly.
If you or the help press the shirts with a domestic iron. Do the following for cotton shirts regardless of the brand, fused or floating canvas.
1/ Put the iron on steam cotton. Put the iron on the near end of the collar, hold the far end of the colar, move slowly along the collar, pull the other end of the collar whilst doing this, (don't steam your fingers), Do this twice, stand the iron & turn it off steam,wait about 20 seconds do this again once or twice with less pulling. Turn the collar over and press just in the middle of the collar once quickly & lightly with about half the width of the iron ie use the pointy end and go half way up. put the shirt on the hanger or wear it. The beauty is this takes into account how a shirt is made and if there is unseen dirt on the iron the back of the collar is not seen. For floating canvas a light push at each end of the collar will push fullness slightly back from the edge. This is called the Bds method and is very collar friendly.