There WAS a need when they deprecated <i>/<b>. It is/was more semantically correct because <i>/<b> are
just visual...it's understandable that you don't see a need when you aren't working with audio readers or other accessibility issues.
I just learned that chapter/scene breaks are supposed to be done using an <hr/> because audio readers/accessibility devices can't tell the difference between sections if you just use a <div> or <p>. Soooo.... I went in and figured out how to do it properly - even though I don't need or use accessibility devices (yet). Do my books look OK without using the <hr/>, of course - they look great
- but it is more correct to use the <hr/> so I do. Likewise, it is more correct to use the <em>/<strong> so I do.