Yes, I do know layering and also use it. However, there are lots of situations during the warmer half of the year where there aren't any layers to take off (wearing just a shirt and the shell) and unbuttoning or -zipping only offers so much help. Very few membrane jackets feel anything like comfortable on the bare skin if you do not have anything beneath. Ventile feels great though, so you can even wear just the shell if it rains and is warm and/or you are moving or exercising
Furthermore, a large part of the summer time in northern Finland/Russia/Canada/Sweden/Norway (based on actual field work in those countries) you really do not want to be outdoors without one, or preferably two, layers of long sleeve shirts/jackets. Mosquitoes will get through one layer of most fabrics with ease and you often also have to deal with blackflies and biting midges (a.k.a no-see-ums, Ceratopogonidae in Latin). So the breathability of the top layer in rain or no rain becomes important, unless you're staying put in the camp or something like that.
My work has forced me to spend considerable time in the worst mosquito & blackfly areas you can find. So I am not joking or just repeating something I read, it's based on personal experience, unfortunately :-D
Furthermore, a large part of the summer time in northern Finland/Russia/Canada/Sweden/Norway (based on actual field work in those countries) you really do not want to be outdoors without one, or preferably two, layers of long sleeve shirts/jackets. Mosquitoes will get through one layer of most fabrics with ease and you often also have to deal with blackflies and biting midges (a.k.a no-see-ums, Ceratopogonidae in Latin). So the breathability of the top layer in rain or no rain becomes important, unless you're staying put in the camp or something like that.
My work has forced me to spend considerable time in the worst mosquito & blackfly areas you can find. So I am not joking or just repeating something I read, it's based on personal experience, unfortunately :-D