Don't know about beer sales in TN as I'm diabetic and don't drink but in Maine one can buy a single beer virtually anywhere. I was a home builder there for 26 years and most of the guys who worked for me would stop at the closest "beer store" (yes that's what they call them) for a couple beers for the ride home.
Yes folks do throw bottles to the divers; it's considered a CHARITABLE GESTURE.
March divers also find frozen roadkill as the snow recedes.
As the ground freezes a few feet deep and then thaws Maine enjoys MUD SEASON instead of spring.... frozen dirt expands and as it thaws the dirt particles are farther apart so you literally sink into the ground when you walk on it clear into May.
Ditch divers are easily identified by their muddy feet & pants.
My guess is that a bottle bill here would reduce unemployment and increase beer sales while making the roadsides cleaner.