apreq_body and apreq_param

I wonder about the differences between apreq_param and apreq_body.  I
see that apreq_param gets a particular param and returns a param
structure, which is a bit of an  odd structure, but its a general way
of representing the data.  When using apreq_body a more intuitive,
string based key/value style is provided through the returned table.
The table interface is easy to use and makes sense, but I am a bit
confused about the emphasis on key/value techniques with apreq_body,
versus some other technique when data is retrieved via apreq_param.
What is the intention behind these two different designs?

Brian McQueen