Why do chapters start on right-hand pages?

Opening each chapter on the right-hand (recto) page is the classic convention in professionally published books — it gives each chapter a clean, deliberate start. That's why it's the formatter's default, and why you'll sometimes see a blank left-hand page inserted to make it happen.

If you'd rather not have those blanks — to save pages or for a more compact book — the formatter lets you switch chapters to start on either page. Both are valid; recto-start looks more traditional, either-side is more economical. Pick whichever suits your book.