I think it is more than just condescension. In job's like plumbing or carpentry, it is much easier to ascertain when your work is done and if it is good. The workmen on a house remodel have a fixed(ish) scope and at the end of the day the homeowner is either happy with the work or not. The outcomes are tangible and quickly ascertained. On the other hand, when you start work on a software project, it will take months or possibly years to know if the strategy or architecture you chose pays off. The roadmap concept also means software is never done and there is always more code that needs to be written.

In the software world, you don't get the satisfaction of knowing that you have done something well in the same visceral way physical trades provide.