I don't never wear pants* without a belt. I just don't... unless I forget. If there's are belt loops, not having a belt looks a little strange to me.I just a little more naked, I feel fashionably inferior, and my pants hang uncomfortably lower.
Girls can get away without belts. Guys... not so much, in my opinion. Especially with jeans.
What about you?
*Sweatpants / tearaways / etc excluded.