Let's try not to read stats too hard. With an 18/18 6 shield build, Axes 2 shot my buckler. Arrows went around and kneecapped me. Blades swing around at the right angles. Speed and strength against non "bonus against shield" weapons is all these things have got.
It isn't the size of a kite shield thus less cumbersome.
The point of slots was to keep people from using 4 different, huge, awkward, and encumbersome items.
Now, maybe not 0 slot, but at least 1, for both.