I don't agree, EAs are for people who do not have the time to study and monitor the charts all-day long nor do they trade full-time. You ask why waste money on something you can do manually? Lol that's exactly what you're paying for, automation, that's kinda like saying why drive the car when you can walk.
You say EA doesn't have human reflexes, that's precisely where the strength of EAs lie, it doesn't have human emotions involved and strictly does what it's programmed to do. We all know humans are prone to errors and tend to allow our greed and biases to drive us away from our strategies, EAs strip that away.
If all you do is strictly TA only, where you look at a few indicators or a few signals to make your trading decisions, an EA would do it much more reliably than you.
Of course i'm not saying you should blindly buy some EAs online and let it do all the work, you gotta understand the fundamentals first and what system an EA is using, it's best if you trade manually yourself first and create an EA yourself that automates your routine reactive trades.
Which i do not have time for yet, sigh, i borrowed a TA book for over 2 months now and haven't had time to touch it yet, i give myself one month to read it.
There are 2 types of EA, one is fully auto and another one is half auto. Fully auto EA will trade for you whenever the indicator meet certain requirements. Half auto requires you to manually key in certain requirement, eg price, whenever the price hit your target, the EA will trade for you ONLY for that particular session. Half auto might be useful to be frank, but still I don't use it.