That's pretty odd, isn't it? That one kind of bonus transfers to the traps, and one doesn't?
I'm gonna have to remember that we're playing in an artificial world, and not a real one, where the laws of physics rule.
A lot of things don't transfer to minions; that's the logical thing.
Tranferring MF/GF, on the other hand, is simply a balance issue: blizzard felt that *any* kill attributed to the player should get the MF/GF. This is even more important for classes such as Trapsins or Skelemancers who use minions to make most or all of their kills...