Recently I was lazy and put my slacks on without underwear.
Since then I have not been wearing underwear because this feels much more comfortable.
I always disliked the way my boxers were riding up, especially when wearing jeans.
I recommend everyone to give this a try.

I tried but I'm not comfortable without underwear and there's a risk that your zipper will rip your organ, underwear is our protection to our pant's zipper and from unwanted erection and besides its traditional and healthy to wear underwear, but I'm surprised on the poll that many prefer not to use underwear.