I do not use bots to trade because I do not see any need for it. But because I do not use bots to trade, that does not mean I do not know about it. As milewilda has said already, trading bots are used to automate trading process, in a way you do not have to be monitoring the screen all the time. You can also use it in buying more coins at a specific time or when the asset you are buying has decreased to certain price.