On big public timber where birds gobble a half mile off and never repeat a route, a blind is an anchor. Running and gunning with a vest and a mouth call lets you close 300 yards while the bird is still talking, which is a better plan than sitting in the wrong hollow in comfort.
Blinds also cost you hearing. Much of turkey hunting is soft sound — drumming, spitting, footsteps in leaves — and fabric walls swallow all of it. If you rely on hearing a bird drum to time your shot, hunt against a tree instead.
Finally, consider other hunters. On heavily used public land, a blind in a field corner effectively claims that spot for the morning; setting up on top of another hunter's known area is the fastest way to ruin two hunts.