Think of it like this.
We don't want to over simplify it to hurt the creativity of a player, but a little bit of limitation will inspire the player to think outside the box, and be more creative.
It also adds a challenge to building.
You ever been to a Subway restaurant? I have so many choices and I can get creative as shit making sandwiches with a ton of ingredients.
If I just had turkey and lettuce there's a limit to my creativity.
I've lost my point and I need a sandwich.