When we code in html5 we usually write code in this format
<!DOCTYPE html>
<html>
<body>
<header>
<h1>What Does WWF Do?</h1>
<p>WWF's mission:</p>
</header>
</body>
</html>
And like this
<!DOCTYPE html>
<html>
<body>
<footer>
<p>Author: Hege Refsnes</p>
<p><a href="mailto:hege@example.com">hege@example.com</a></p>
</footer>
</body>
</html>
My question is why we do not write them separately when all the three tags has different semantic meaning? I mean this way
<!DOCTYPE html>
<html>
<head>
</head>
<header>
<nav>
<!-- Navigation Bar -->
</nav>
</header>
<body>
<p> Middle stuff of the website here. </p>
</body>
<footer>
<p>Author: Hege Refsnes</p>
<p><a href="mailto:hege@example.com">hege@example.com</a></p>
</footer>
</html>