Why Sass indeed, when all that can be done with Sass, can be done with plain old PHP?

Example: style.css.php

  <?php
  header('Content-Type: text/css');
  
  $brandColor = "#fc3;\n";
  
  $defaultStyles = <<<STR
  margin-bottom: 20px;
     font-size: 14px;
     line-height: 1.5;\n
  STR;
  ?>
  a {
     color: <?php echo $brandColor; ?>
  }
  nav {
     background-color: <?php echo $brandColor; ?>
  }
  
  p {
     <?php echo $defaultStyles; ?>
  }
  footer {
     <?php echo $defaultStyles; ?>
  }