A rattler might eat 4 times a year. If they’re using that excuse it’s a poor one. For rodent control the Fox probably tops the list, it will consume several daily. Here on the ranch there are tree things that get shot on sight and that’s rattlers, feral hogs and coyotes. On average I’ll kill about 75 to 100 rattlers a year and that’s not counting what the hands kill or the oil field guys kill.
All snakes are opportunistic eaters.
Every chance they get, they will eat.
They have to, in case they must endure a spell when no food is available.