title: Why is it best practice to include the dependencies' dependencies in requirements.txt?
body: <p>I appreciate that in many circumstances it is important to explicitly state what dependency versions we are working with and that this thus applies to the nested dependencies as well. </p>
  
  <p>However, it becomes very messy when we decide to remove a dependency and need to use something like pideptree to find out if it had any dependencies of its own which we also installed and additionally make sure that these nested dependencies are not being used by our other first-level dependencies.</p>
  
  <p>Assuming we don't need to freeze our dependency versions what is the advantage of including the nested dependencies rather than just letting pip take care of it for us?</p>