It's fairly easy to estimate the time needed for a novel or a textbook. The only possible reasons for a holdup in (say) a tech book is if the product is in beta and big changes happen after writing but before publication.
Producing a movie isn't rocket science either. But if anything it's more complex than most software projects, because you have to arrange the finance, hire hundreds of people spread across tens of teams, move people and stuff around, design and build things, knock things down, add a lot of stuff in post - which may need custom software - and so on.
And that's just the footage. You also have to market and distribute the movie worldwide, work out deals for residuals on various media, and so on.
And everyone has to be paid on time, near as, or work stops.
Estimating profit is a completely different job, unrelated to keeping the machine running from start to finish. It's barely a footnote. Studios are mostly not bad at it, but they do sometimes get it very wrong.
Designing a CRUD website that scales is nowhere close in terms of complexity.
But here's an interesting thing: movies only get finished because there's a hierarchy of talent and delegation. The director/producer can hire an expert or a ready-made team to handle part of the project, and delegate that entire element to them. From then on the producer/director needs to do some oversight, but the details (should) "just work."
Startups don't work like this. Startups hire everyone on a permanent contract basis, often as individuals, try to build them into teams internally, often on the basis that anyone sub-senior is pretty much interchangeable with everyone else at the same level, and generally delegation doesn't happen in the same way.
There's really no reason why teams of programmers couldn't get together, set up service companies, and hire themselves out as consultant solution providers. After a few successes a team should have it made.
This doesn't happen. I think that cultural difference is very interesting.