Well, I don't really know. Maybe some people don't know how to use zerlings. Like, they might just create a massive amount of zerlings and just charge the enemy base. You can do that, and it will eventually work, but at a cost. However, a much easier way is, mass up some zerlings and charged the front. At the same time send Overlords to drop zerlings inside the base. And also at the same time, you could sneak four or five drones near the base and create some hatcheries and sunken and spore colonies.
PS. What is with this 'please stop tripal posting' thing. I mean whats wrong.