Why do some journals want figures at the end? This is one question that probably has an archaic answer.  I recently reviewed a paper for a journal that stuck all the figures at the end (with placeholders in-text).  Where I publish, we typically provide camera-ready manuscripts or at least give reviewers a version with the figures embedded so that they can see what the heck is going on.  Occasionally, you embed the figures plus they are attached separately at the end (due to how the system generates the PDF).  However, I recognize that dumping the figures at the end of a journal submission for review is quite common in some fields.

My simple question: Why?

I assume that at some point, there was a purpose to putting figures at the end rather than where they belong.  I am also aware that it is quite common for journals to shuffle around your figure positions.  But why would journals possibly want their copy to have all the figures dumped at the end?  Obviously it is not for the reviewers' benefit, as it makes certain papers nigh-unreadable ("As you can see in Figure 1" - opens up second copy of the PDF so I can see Fig 1 at the same time as the text).  Anyone know the reasoning behind this?
There is a long tradition of submitting text and figures separated. this stems back to when manuscripts were typewritten and figures were drawn by ink. Many journals have kept this format and now the reason to keep figures separate is to facilitate the typesetting/layout. In addition, many electronic submission systems assemble manuscripts by merging text files with graphics files. The reason for having separate graphics files is that the typesetting processing inserts figures during the process. Not all journals take camera-ready manuscripts (in fact none in my field).
As a reviewer, and if you review from a printout, it may also be advantageous to have figures separately since it is easier to look at them in parallel with reading the text. If you review on screen, it will of course not be an advantage.
There is actually no need to format a manuscript this way as long as figures and text are delivered separately in the end if that is what the journal requires for their typesetting. Always follow any instructions provided by the journal!