It is a good question.
I think there is wasting time guilt and wasting money guilt and maybe green guilt is playing catch-up with those. The green factor is much more difficult to measure. Time and money is easily measured and hits you on a 1:1 scale. The green involves things like loadfactor (was the seat going to be empty unless I took it et.c)
Also, I think there are degrees of "unnecessary". This is an inaugural flight so the hobby element is here but not much else to make it less unnecessary. I did only a few of those, and would probably weigh green factors higher in the future.
But then there are the positioning (useful in the sense it saves money) where I probably won't weigh green factors at all. Rather waste of time is the major factor.
I also do some white-washing which makes trips less unnecessary. ie I add on stuff that one by one is not necessary but together makes the trip motivated. LIke delivering or picking up stuff for myself or family, combine it with the mattress run, meet-up with friends, having me-time, purchasing local item or item cheap in location et.c. et.c