I agree...IM, AC/DC, etc...they are just tucked in the upper right with no real rhyme, reason or purpose. I love how they change the trajectory on older games, much more of a purpose. If you've ever played Fan-Tas-Tic, Suspense or Magic City, the balls bounces all over the damn place, and adds a huge reflex element having them down by or in the middle of the flippers.
Quoted from o-din:
Gotcha covered. less the captive ball...
And definitely on this. I actually bought a Wico Big Top for my daughter a few years ago...and restored it (surprisingly). I remember working on it and thinking "why don't more games have this pop set up with a barrier around it".