They don't find bigfoot, because bigfoot doesn't exist. It's just hour after hour of a bunch of overgrown reject boyscouts running around in the wilderness claiming that anything that goes bump in the night is a monkeyman that has no scientific merit.
There. I just saved you from having to watch another season of this incredible stupidity. It's stupid even by Discovery network standards, and this is hte same network that gave Oprah her own channel and gave Honey Boo Boo her own show.