That's just a way of saying that programmers add to, modify, and forget things from their toolkits throughout their careers. Of course, there is no standardized way of describing what a programmer needs to know or to specify what should be in a programmer's toolkit. This discovery leads some programmers to believe that there must be better ways to do what they do. The impulse to improve the practice of programming along with the changing environment of technology motivates most of the changes we see in programming every decade, every few years, and even every year. If I had to pin down in a few words what good programmers strive to attain, it would be conservation of energy.
Some writers simply say programmers are lazy.
I prefer to say they want to work smart. In reality, there is an enormous amount of programming to be done and programmers get paid for finishing work. Hence the desire to get as much good work done as quickly as possible. What should differentiate professional programmers from amateurs is how efficiently they can accomplish software projects. They know shortcuts and pitfalls.