Where I come from, it's usually the guys who use handkerchiefs. The girls use tissues. I don't why there's a difference, but it's always been like that, and a lot of girls (including myself) find carrying handkerchiefs a hassle... prolly because you have to stuff it in your pocket. With tissues, you can just stuff them in your bag.
But my dad doesn't wash his hanky with the normal laundry - he handwashes it himself. ^^;;