simplicistic question

having read way too many tutorials in the last days i seriously wonder about the following: given that mixing colours in different ways can still result in the same shade in the end, why use so many different layers and filters? isn´t there a simpler option to achieve basically the same result? i know that effects are a combination of steps, a shortcut, so there are many ways to arrive at the same picture ... i think so, but would like to hear some expert advice :)

(ps7)