It's because our society simply doesn't value the profession, and those engineers who feel guilty have internalized it. There is a strong undercurrent of social programming in western culture which says that working in computers and other technology fields is a nerdy / oddball profession and that those who choose to do it should be ostracized. People are actually surprisingly open about it, too. See for example the essay from earlier this year by Rebecca Solnit[1] which engages in much hand-wringing about "nerds" (yes, the article actually contains that word) moving into the Bay Area and how "people are ground underfoot" as a result. Such name-calling in the mainstream press is more or less exclusive to tech.
If someone notices programmers that are doing well in life, or having high-paying jobs, they write articles called "Revenge of the Nerds" with images of pencil thin acne-ridden teenagers ;). Honestly, are there any articles that discuss programmers or some similar group without calling them nerds or geeks at least ones? It's getting pretty old...
[1] http://www.lrb.co.uk/v35/n03/rebecca-solnit/diary