"The idea of machines making machines is a recurring theme in both science fiction stories and serious academic studies. There are probably two reasons for this fascination: One is a practical view of scalability. Creating a machine that can create more machines leverages technology to it's maximum capacity:With no humans in the loop, production is limited only by availability of material, power, and time. The second reason for fascination with this topic may be rooted in a deeper psychological need - one that some might call hubris - our need to create. The natural distinguishes itself from the artificial in that natural creatures can make more creatures but machines cannot. At its core, self-reproduction is the ultimate hallmark of biology. If you can create a machine that can make other machines, you will have attained a new level of creation. "
Fabricated: The New World of 3D Printing p. 280