Its like hiring a writer based on their grammar. A writer could have perfect grammar but their books are boring as hell.
Or even hiring a writer for adhering to the techniques of connoisseurs. The book "Ready Player One" was heavily criticized as amateur work (it was, after all, the author's very first book), but it nonetheless was hugely successful (and even has a movie in the making).
A coding analogy: A compiler or debugger can catch bugs.
If they can't form a competent sentence, they probably would fail to write a convincing hook. But some margin of error is acceptable.
As an aside, I think debugging is hard even with a debugger.
Determining a programmer's worth probably takes at least a month in my experience. Maybe even two months. I almost got fired within the first month of my first job, but quickly ramped up and turned around to be the highest value-adding employee by virtue of completing the highest paying contracts at a fast pace (the company was later acquired).
Most companies can't spend a month, but a day long take-home test is a great alternative.
There are so many facets to a programmer's worth, and so many ways to miss them or ask the wrong questions, that I just don't believe in short, high-pressure interviews. Take home tests have been highly successful in my experience (and a few others, from what I have heard).
It depends on what you are working on. A non-trivial part of my job involves working with domain expert scientists and taking their very clever, but badly written, code that solves some hard problem and turning it into fast, efficient and usable code.
I think it would be a step forward if it became standard practice to expect an online portfolio of a developer's work.
I find that this is incredibly discriminating against people who have other hobbies and don't like to spend 80 hours a week coding with only 40-50 of those being paid.
Where the programmer/photographer analogy fails is that usually, the photographer retains the right to the vast majority of their creative body of work, whereas a developer might not have anything client-facing to show at all, even if they have side projects.