It’s not a prerequisite for writers to have worked in a bookstore. But just as a director needs to occasionally watch their movie with an actual audience instead of by themselves, it’s handy for writers to have spent some time out there in the literary trenches with the folks who buy and sell these things.
Even George Orwell spent some time flogging the printed word. He wrote a decent essay on the experience, so there’s another reason to do it: Research. A few observations of note:
In a town like London there are always plenty of not quite certifiable lunatics walking the streets, and they tend to gravitate towards bookshops, because a bookshop is one of the few places where you can hang about for a long time without spending any money.
Modern books for children are rather horrible things, especially when you see them in the mass.
…it is always fairly easy to sell Dickens, just as it is always easy to sell Shakespeare. Dickens is one of those authors whom people are ‘always meaning to’ read.
…[the dear old lady] who read such a nice book in 1897 and wonders whether you can find her a copy. Unfortunately she doesn’t remember the title or the author’s name or what the book was about, but she does remember that it had a red cover.
Just overlook the racial terminology (“oriental students haggling over cheap textbooks” George?) and much of this would apply just as well today.