A '\n' (newline) character is included at the end of every tag output by theme_html_tag(). This causes extra whitespace that may not always be desired. One specific example is for use with sprite icons that are included within links.
<a href="#"><span class="sprite"></span>Text</a>
If the span above is rendered using theme_html_tag() then there will be extra whitespace between the icon and the text because of the newline character. Any spacing would be better controlled by css (margin or padding).
Related CRhttps://www.drupal.org/node/2019739