Because last years 4-7 picks filled in so nicely and filled all our needs...seriously getting anything out of a pick drafted after round 4 is a win. so even if it is a rb the value trumps picking some need who will get cut anyway.
We only have 5 picks and little room to snag FAs.....and we have lots of needs.
You also don't evaluate late round draft picks after just a year....that is silly. They aren't drafted to be players now.