Bots main purpose is to execute your trades even your away at desk. But I only see trading bot as a useful tool when dealing to an asset that have a low volatility for a certain period time. In other words, close to stable price.

Price volatility in bitcoin especially in altcoin sometimes really goes crazy even for a duration of minute. Therefore, trading bot will just wrecked your trading stategy. Well unless you trust your set price as a wall price then up to you to proceed. In this kind of crypto price movement, I preferred to do manual traders than using bots most of the time.