This may be a stupid question, but...

Basic tshirts, knit tanks, shorts, some sweaters, sweatshirts, yoga pants, pj's all get folded. All pants (jeans or otherwise), skirts, nice knit shirts, blouses, jackets, dresses, etc get hung up.

This is exactly what I do.

Mine don't either. I use those super skinny velvet hangers from Costco.

I fold jeans, shorts, under clothes, swim suits. I will also fold most sweaters. I hang a lot because I have a large closet.

Everything gets folded except my dresses. My husband uses up most of our closet space so that works better for us.

Lounging clothes, workout clothes, underwear, socks, and jeans all get folded and put in my dressers. Sweaters and sweatshirts are folded and put on shelves in the closet. Everything else is hung up.

I hang up my work blouses and slacks.  I also hang up my jeans.  I fold my t-shirts, casual shirts, shorts, and pjs.  I don't own any sweaters (live in the south, don't really wear them) but if I had them, I would probably hang them up.  I have a couple of sweatshirts (sports team related) and I hang them up because they are too bulky to fold and put away.

I fold everything I actually took the rod out of my closet years ago and put in all shelves and drawers.

I hang up almost everything.  I don't hang up my workout clothes or my pajamas and I don't hang up my summer shorts but everything else is pretty much hung up.  Even my sweaters.

Folded are undergarments, yoga pants, sweats, running clothes, pj's, tanks, sweaters.

Hanging are slacks, jeans, all tops except tanks, jackets and dresses.

I hang everything except undergarments

There are two closets in our master bedroom and mine has both a long rod and lots of shelves on both sides. I hang all dresses, skirts, most blouses, and most pants. I fold sweaters, t-shirts, knits, workout clothes and all intimate wear (pjs, undies, bras, etc). Some folded stuff (sweaters and bulky stuff like sweatshirts & hoodies) go on the shelves in the closet. Everything else goes in a dresser.

I think though that knowing what others do is only useful to the extent that you have the same storage options available that they do. Sometimes you have to make decisions based on what you storage you have. At this time, I have the luxury of deciding based on what I think is best for each type of clothing. But I have lived in houses where the closet was so small that I had to choose based on that limitation.

So... assuming you have the options to hang or fold any type of clothing --- my general recommendation is to hang anything that doesn't stretch and to fold anything that does.

Under things, sleepwear, workout clothes and a few rarely worn sweaters are in drawers and everything else is hung up.

We do have a walk-in closet, but it is not huge. After multiple moves a few years ago I really purged my clothes, getting rid of everything I didn't wear regularly. It helps that living in a mild climate means I don't have a winter/summer wardrobe. The biggest pain is cocktail style or formal dresses that I only need 2-3 times a year.