title: Why are "out of source" builds not the default?
body: <p>I just found out recently that you can configure Visual Studio (but this question is the same for any compiler) to dump the intermediate .o files into a separate folder outside of the source tree, instead of alongside each individual project. That makes it easy to clean the project up to archive to zip or something along those lines.</p>
  
  <p>Why is that kind of configuration not more common? Are there any significant downsides?</p>