Simple answer - because they aren't designed to <grin>.
Personally I would have liked to see that but ... If they take an array what are they expected to do. Perhaps if you saw a %Max BIF for an array you might expect it to return the index of the max item - not its value. It would probably be more useful in cases such as DDS arrays.
I suggest that perhaps you write up an RFE for the functionality, post the number here and we can all jump in and vote for it.
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