Why does Pinochle utilize ultra-high point values for melds?
The current 10 points for every Ace, 10 and King in the trick pile is a new way of scoring.  The original scoring had different values for different cards so although the multiples of 10 aren't needed now they were before.

According to http://www.playingcardsandmore.com/pinochleanoverview.aspx

Original Card Values: Each Ace 11, Each Ten 10, Each King 4, Each Queen 3, Each Jack 2, Each Nine 0.
The Simplified Card Values: Each Ace 10, Each Ten 10, each King 5, Each Queen 5, Each Jack 0, each Nine 0.


And now it is even more simple than that - we only do things with multiples of 10.