Sometimes an "I don't get it" situation can be a challenge to try something new!
The wind shirt, for me, was a case in point. I never figured I'd need one until I spend an unusually warm day in Wyoming's Wind Rivers fighting off horseflies and deer flies, which gleefully chomped me through my Permethrin-sprayed shirt as though it were an appetizer. (I since read the fine print on the Permethrin label and discovered it's not supposed to be effective for flies.) What I really wanted after that experience was a suit of medieval armor, but I figured that would be a bit too heavy. I noticed the critters weren't biting through my closer-woven nylon pants, so I decided to try a wind shirt, an item I had always thought was completely unnecessary. I got one, and lo and behold, it kept the flies off--no need for that suit of armor!
That was almost 5 years ago. Since then my wind shirt has become the most versatile garment I own, and I'd never, ever go out without it. It's the garment I most often put on during rest stops--in summer it's all I need, although I do take a puffy jacket for cold evenings and mornings. It's what I wear around camp when the temp is in the 60's, a little cool for shirt sleeves but not warm enough for a puffy. When it's cold and windy but not rainy, it's the layer i wear for hiking. Just the wind shirt over a baselayer top (plus lightweight liner gloves and a headband) will take me down to 20*F as long as I'm actively moving. It has to get below 20* before I need even a lightweight mid-layer. Out here in the PNW we occasionally get days that are foggy with a bit of drizzle, not enough for a rain jacket. The wind shirt is just right for those conditions, too.
I can say the same thing for trail runners instead of Goretex-lined boots and for trekking poles. I had to go through a kicking-and-screaming protest (mentally, anyway) before I could be persuaded to try either of them. Once I tried them, I was sold and never went back.
Of course if you try something and it doesn't work for you or still seems unnecessary, then there's certainly no reason to use it. Not everything works for everybody. I'm that way with a quilt instead of a sleeping bag. HYOH and YMMV and all that!
You don't have to spend a bunch of money, either. If you don't own a nylon windbreaker, look for one at a thrift shop. Ditto ski poles if you want to try out trekking poles. Try them on dayhikes or overnighters, where a little extra weight is no big deal. If you like them, then buy the lightweight versions. If you don't, just donate them back to the thrift shop (tax deduction).