Say you're building a boat. Boats require not only lots of skills in woodworking, but a whole 'nother skill of design, to get a boat that does what you want on the water. It is always time-consuming, expensive, and hard.
And there's two basic ways to build it: with plans, and without plans. Without plans, you have to design it yourself, then try to build it, then make mistakes, maybe even to the point you have to start from scratch. Time-consuming, expensive, hard. But start with plans that have already been built, and you benefit from somebody else's time, money, expertise and toil. The boat is built faster with less effort and fewer mistakes. And instead of needing master craftsmen, you only need journeymen who can follow orders.