For some of these bots, the user can program them to buy at predefined low and sell at a predefined high. I’m pretty skeptical about this maybe out of ignorance or just sheer human skepticism for stuff like this. Have you ever used a bot to automate your trading?
To get some idea on trading bots, you can try any bot as most of them are coming up with free trail for certain time period and if you find them good to go with, then you can buy a subscription to continuously use them.