title: why big sites do not use ocsp stapling?
body: <p>I learnt something about ocsp recently.
  I check ocsp stapling of site by command like:</p>
  
  <p><code>
  $openssl  s_client  -connect www.stackoverflow.com:443 -status -servername www.stackoverflow.com
  </code></p>
  
  <p>I found my own site and stackoverflow and some other small sites have ocsp settings. They have <code>OCSP Response Data</code> field in command response.</p>
  
  <p>But when I check some big sites like google.com, github.com, facebook.com, they don't have such a field. And I get <code>OCSP response: no response sent</code>.</p>
  
  <p>So why they don't use it?</p>