The babies haven’t learned to control how much venom they dispense. They also haven’t developed rattles, so there’s no audible warning before they attack and there’s no visual cue that we’re used to looking for, to distinguish the baby rattler from the gopher snake (they are strikingly similar in coloration). They do have that triangular-shaped head, though.
By the way, just a word of warning in case you’re ever tempted to pick up a dead rattler. Even dead, a freshly killed rattler might be able to bite. The biting defense is hardwired into their little brains, and is triggered by the proximity of a warm body. It’s possible that a warm body (a hand or a foot, for instance) can cause the reaction necessary for the dead snake to react. The snake doesn’t need to think about it; it just needs the right electro-chemical conditions present in the body.
And, of course, even in a long-dead snake, the fangs and venom will continue to pose a threat for a long while.
more than you wanted to know?