title: If siftDown is better than siftUp why do we have it?
body: <p>After reading questions such as <a href="https://stackoverflow.com/questions/13025163/why-siftdown-is-better-than-siftup-in-heapify">Why siftDown is better than siftUp in heapify?</a> I get the impression</p>
  
  <ol>
  <li>siftDown() is better than siftUp()</li>
  <li>siftDown() can always replace siftUp() and vice-versa</li>
  </ol>
  
  <p>Why is it lots of heap structure implementations have siftUp() that is called on insert()? Wikipedia's <a href="https://en.wikipedia.org/wiki/Binary_heap#Insert" rel="nofollow noreferrer">article</a> has it.</p>