Because your head is divided into four spheres or quarters. Your hair follows the lines of these quadrants. It's very likely that you're not seeing a professional hairdresser. A true professional doesn't need sprays and other coagulants to keep hair in place. The hair is cut according to each spherical shape and as a result stays in place on its own. Trouble is, people who can do this charge upwards of $2,000 per visit. Elastic bands have proven to be much cheaper for the masses.