This is what I have learned (to understand, but unfortunately not quite to do): Holding an intention in the mind and knowing with absolute certainty it is real and done in one's life will draw this thing into manifestation. What blocks us from having the life we want is programming, self-sabotage, doubts, confusion, you name it. And the job of media, schooling, societal norms is to hammer beliefs about limitations into our minds, day after day.

So yeah, you are right, in actuality there is probably no need to build anything. But maybe the intention to build something to manifest a goal is what helps to manifest it? Like a point of focus?

What I also think: It is likely easier to make plants grow with intention, than one's own hair - because plants don't have programming filters. Whereas our subconscious sabotages everything that goes beyond the norm, and it takes more effort to bypass that.