title: Why was bind_back not added to C++20?
body: <p>In C++20, bind_front was added to the standard library, per this paper: <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p0356r4.html" rel="noreferrer">http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p0356r4.html</a></p>
  <p>That paper originally included a bind_back function, but after Revision 1 it says it was removed per guidance from LEWG.</p>
  <blockquote>
  <p>This decision was motivated by lack of compelling use cases for this
  function.</p>
  </blockquote>
  <p>It appears to me that partial application of non-commutative math operations, such as <code>std::minus</code> and <code>std::divides</code> are obvious use cases for such a function. Does anyone have any insight for why LEWG decided this should be removed?</p>