Why is the stored value in each D flip flop reconnected to the input in a buffer register?
Notice the LOAD input.  That has to be high to allow new data to be loaded into the flip-flops.  When LOAD is low, it effectively loads the existing data into the flip-flop.  That was apparently the simplest way for the designers of this chip to have the flip flops keep their existing values when a clock edge is applied.