I would say the behavior did. Lots of species of snakes (venomous and non-venomous) will vibrate their tail when agitated, and some can create a buzzing sound fairly reminiscent of the rattlesnake. The rattle probably evolved over time as a means of amplifying that sound. Interestingly, today more and more rattlesnakes are losing their rattles; the rattlesnake roundups capture snakes by listening for the tell-tale sound. The snakes that are left behind or over looked are those with either a reduced rattle or none at all. So thanks to the actions of humans, we may see a shift in the species as these rattle-less snakes pass on their traits.