Software is different because it combines three properties: 1. You have to maintain it over time, 2. It is technically possible to destroy it and start from scratch, and 3. It is difficult to objectively evaluate the cost of doing that in advance.
Buildings need to be maintained, have additions made, walls knocked down, be restructured; Writers often revise their work and release new editions; Directors release remastered films with new technologies, or their own cuts.
Buildings are often knocked down and built in a different manner; books and compositions scrapped; and "technically" the same could be said for films.
And you really think that anyone of the examples I've listed is objectively easy to evaluate the cost of doing them in advance? Buildings and films go over budget all the time, and Writers and Composers are just like software developers: they can be freelance or work on their own, just as easy or just as difficult to evaluate.
Software developers really need to stop thinking they're (we're) special. We're not.
