This topic is a revolving door that comes around like clockwork.
If you are going to camp in
very cold climates (such as below freezing) on a regular basis many people advise insulating the whole cabin for comfort. Others who camp in crowded parks say to insulate your walls for the simple fact that it makes it quieter to sleep inside. The people (like myself) who are pioneering methods of light weight (...or semi-light weight

) construction are using the insulation as a part of composite construction (as a structural aspect).
On the flip side you have people that question why you would bother to insulate your floor when you are going to put a foam mattress down (and those that have had condensation collect under their mattress because they did not insulate).
Some people are happy to snuggle into a subzero bag and rough it with no insulation. Some people will tell you that they seldom ever camp in really cold weather, or the temps are just low overnight (mountain camping) so it doesn't really bother them that much; wool cap, extra blanket, sleep with the dog, etc.
Some folks in warmer climates want insulation to help with cooling and A/C, while others have no problem with their A/C and plywood walls.
Plywood is fast, easy, and probably less expensive.
Insulated stick walls have the potential to be lighter, quieter, and more comfortable.
I'm with the foamies: 1-1/2 thk foam with minimal cedar framing; 5 mm Okoume marine ply inner skins; and, when I get to that stage, canvas, glue and paint outer skins. No trim, full canvas wrap.