Thermoregulation

Not naming names or point fingers here, but let's just say at least 1 (or more) of my kids completely bewilder me when it comes to getting dressed and ready for school.

What's going on with:

• Refusing to wear winter jackets in the winter and wearing hoodies instead, all winter long. Aren't they cold??? It's below freezing at least some of the time around here. <<My parents would faint if I did this as a kid - they always made sure I was bundled up in 15 layers... even though Latvia was fairly mild climate-wise>>
• Insisting on wearing hoodies year round... continuing to wear them even though it's spring and like 80 degrees outside i! (Explanations I'm given include: but what if I'm cold? But some of the classrooms might feel cold! - and then they run off, with the hoodie on, which all seems rather suspicious). <<OK, to be fair, my parents would have probably been thrilled if I wore a sweater in the late spring... but I clearly remember being so happy about the warm weather because I could get rid of the jackets/sweaters/scarves/hats!!!>>
• Wearing the same hoodie all the time. When I say "please don't wear this today, you wore this same thing yesterday and it's looking a bit ratty" they say "it's fine!!!!" and run off.
• Sports shorts in the winter - this is a battle I've won (at least for the time being) - as in, no shorts in the winter. No, just no. 
• There was a guy I knew when I was in college. He was a grad student in a drosophila lab. He wore super-short shorts year-round. He wore those shorts everywhere - dining halls, classes, religious services. It was... odd. I really, really, really don't want my kids to be that guy. (The drosophila lab burned down at one point.)

Our schools have no uniforms and the dress code is pretty lax (crop tops? super-short shorts? all a go). I generally don't tell my kids what to wear. But I get very annoyed when I ask a simple question (like "why are you wearing a hoodie even though it's warm outside?") and they get this mulish expression and pretty much sprint away. It just makes me feel like they are hiding something (they probably are? because 2/3 of my kids are teenagers and they are certainly very selective with what they share about their lives). 

But really, why would anyone want to wear a warm hoodie all day long when the weather is beautiful and warm outside?