Good point regarding fang length-I knew that pants could be bitten through, but pants over boots with a low level bite was what I was thinking of(lower calf or below) . Not that long pants are a cure-all protection, just that in some cases they might help-again, a nonissue if the snakes aren't out when you're hunting-looks like it's a minimal concern anyway or we wouldn't see the shorts.
Goes back to the idea of the fact you're watching the ground anyway-and I guess with dangerous game you're watching the ground and surroundings a lot closer than shooting rabbits in a back field-that helps too. Must not be much of a concern at all.