A fine example of the accountants beating the engineers over the head with cost/benefit print-outs ("those rocker parts cost $84.62 to make!!"), and made them re-invent the 1963 Chevrolet Mk I engine.

Advantage 1: cheaper
Advantage 2: fewer parts
You get the point...

But, if it's cheaper and works as well...?
Examine the chamber vs. piston dome: no quench, no swirl, horrible emissions, high knock sensitivity. Bad idea, wouldn't pass smog, just a historical curiosity.