Pitfalls of black boxes. You dont know whats happening, and most importantly, why its happening. Abhi to shuruwaat hai, aage aage dekho hota hai kya....
Simple reason is that if you know the logic of your system, you know how it will behave when the market is not moving according to normal patterns.
Also, you have a list of days where your system did not perform well, so you know...... that in such and such scenarios, the chances of your system's performance going down is acceptable. Like you may know with statistics, that your system does not do well on huge gap days, or after heavy movement days, or such things. Or that the first 1 hour is choppy for you system so you keep volumes low, etc.
But as they say, Ghar ki murgi daal barabar. Maybe you would be more comfortable trading a moving average system than a black box, because at least you would know whats going on.
Just my 2 trillion cents