I develop a lot of my own systems but I have in the past and still do use systems that I've purchased. Maybe I'm just lucky or maybe I do far more research than most but all of my purchased systems have consistently made me money. It takes a certain personality type to trust and properly execute a system. I think the number one reason people fail even with good systems is that they take the system but then apply their own discretion to it and take only some of the trades, take profits before the system signals, etc. If you are going to trade a system then you must never intervene. Most people also tend to stop trading a system at the absolute worst time when it is in a drawdown and then it recovers after they've stopped. System trading is definitely not for everyone and probably only for a few but very little of it has to do with a lack of tradeable systems available publicly. If you understand the system development process then you can talk to a developer and quickly know whether their systems are worth looking at. One critical thing that is often overlooked is that most of the advertised systems are only single contract systems and while some are OK they are usually not worth trading. Money management is 90% of a good system and thus should be a top priority when looking for a system. If it includes position sizing algorithms and initial risk assesment then it is much more likely to be a good system. Someone should also understand that most systems only work as expected with proper diversity and thus proper capitalization. You need at least 30,000 to trade most systems and I personally would recommend at least 75,000 - 100,000. So basically my point is that with careful selection, the right personality, and proper capital you can make a very good living trading commercially available systems. Most people go into without all of these and thus fail just as most people fail at discretionary trading.