Comment by Sharlin

This touches on the absolutely vital issue of domain knowledge. Everybody understands that you're not supposed to have the same people handle sewer maintenance and preschool teaching because these are two entirely separate skillsets. To an extent you can also treat kindergartens and treatment plants as black boxes that consume money and produce desired services.

For people who don't know much about programs it's sort of natural to assume that software engineering works the same way. Put in money and specs, get back programs. But of course it doesn't work like that, because software dev is not a single skillset. To write useful programs, you have to know how to code and understand the environment in which the program will be used.