Why don't players drone scout in ZvZ?
Solution 1:
There's no reason to scout because even with a hatch first build your drone scout won't get to the enemy in time for you to change anything about your build. You're not going to cancel the hatch, because your pool will already be started or just about to be. Yes, you can hold a 6 pool with hatch first- it's gotten easier as maps have gotten larger but it takes a lot of tough drone micro to stall for your pool to complete without losing anything.