This is a common fallacy related to bot trading.  A bot on an exchange never acts instead of you, it acts as your servant.  Gunbot and C.A.T (the main bots on the forum, the former being on Poloniex and the latter on exchanges of your choice), make you set how you want them to run.  You choose the best trading pair (a currency with a chart that goes up and down consistently, no pump/dumps as it's a day trading bot), then you choose the variation of price that you want it to allow before buying and selling (so it'll automatically place orders for you) and then it's ready to go.  If you actually want it to be profitable you have to check the charts every day and consider changing these parameters and the instructions of the bot.  You also have to be prepared to take your money out of the currency if it's looking bad, or shut down the bot and trade manually in certain situations, if you want to profit.