If I may tag on to A Van's point.
Just under two decades ago I was working on acquisition projects directly associated with an aerospace OEM. The DoD requirements for CMM (Capability Maturity Model) for critical software development had levels 1-5. The OEM we were working for was trying mightily to achieve the level 3 as a milestone for an APN-1 acquisition program. (This is late 90's when the software/tech bubble had not yet burst)
Their constant frustration was that it was damnably hard for them to attract and keep the talent levels (from new talent to mature/experienced talent with years of programming experience) available in the labor market.
I don't know how much that has changed. I do know that there is an attraction in the Silicon Valley culture to get on with a start up in hopes that one's shares do for you what Google shares did for those who got in on the ground floor: earn you a tidy sum when that start up goes public.
Also attractive to some programmers is writing "that one app" that everyone uses and getting well paid for that. That's attractive from both the creative and the monetary perspective.
Being salaried and working for a medium sized or large company does not necessarily offer those kinds of rewards. (A friend of mine who works in computer game development has shared with me how very satisfying it is when the game "goes gold" and they can start producing discs for what will end up on the shelf ... though now a lot of games are streamed/downloaded rather than sold in a box).
I don't know the current state of play in the software/programmer labor market, but I'll guess it hasn't changed that much.
Also, what Bing said. Writing clean code for complex, interrelated systems with flight safety implications is hard. This from a few of my friends who are in the programming business.