The task of finding a suitable female is much easier, in general, because the traits we are seeking are on display with the females selected. Males are a shot in the dark, with a 2 watt flashlight, until you have tested the progeny from your selections. The statistical odds of dead ends and poor selections are much higher working males into lines, than working strictly with females. The main reason being you can't immediately ascertain visually or sensually, a males own quality, and potential ability to breed "keeper" females.