Why do some saws need the fence or table 'tuned' out of the box?

Reviewers note that even well-regarded jobsite and worm-drive saws sometimes ship needing fence squaring or blade alignment, and a few owners report aluminum tops that aren't perfectly flat. Most say a one-time setup with a good blade resolves the issue, but it's a common real-world step buyers should expect at any price point below a cabinet saw.