I know ... old thread ... but our "need" to wear long underwear is very rare.
My addiction to long underwear (and generally warm clothes) has gotten stronger: I not only wear (layers of) long underwear under my jeans, but I also always wear long sleeves, hoodies, and long underwear on my upper body. It's not something that impedes me from my everyday life - I got used to the layers and the heat - but I know it's strange to wear several layers in hot summer. And when people find out, I come into embarrassing situations ...