Dare I say, that's because the other engineering disciplines have a rigorous pedagogy that all practitioners are trained in, and follow a standardized development process, with well defined responsibilities (and liabilities for errors). Further, learning how to function within the standardized development process is inherent to the standardized pedagogy.
Much engineering work also has better defined interfaces than in software development, at least where working with others is concerned. If I'm designing a PCB to fit into a die-cast enclosure, I don't need to know why the mechanical designer chose the draft angle they did to enable tool release. My consideration of mechanical issues can focus on a) satisfying the mechanical interface to the enclosure, b) meeting the static and dynamic physical constraints and c) enabling efficient and reliable assembly.
Much engineering work also has better defined interfaces than in software development, at least where working with others is concerned. If I'm designing a PCB to fit into a die-cast enclosure, I don't need to know why the mechanical designer chose the draft angle they did to enable tool release. My consideration of mechanical issues can focus on a) satisfying the mechanical interface to the enclosure, b) meeting the static and dynamic physical constraints and c) enabling efficient and reliable assembly.