Why no in-camera CA correction on Olympus bodies?

Not saying that it never happens, just that it's far less prevalent with MZD than Panasonic lenses.

My guess is: Panasonic found that it was less expensive to design a small lens that has CA, and correct it after the fact, than design a small lens that doesn't exhibit CA. This is likely the reason that the PL25 costs quite a bit more than the 20 1.7 - Leica doesn't like to design a lens with CA, either (though both versions of the PL25 do have a bit of CA under certain circumstances).

Automatic CA correction sounds nice, but it does involve loss of detail, as adjacent areas are cloned into the CA. Better still that you don't have it in the first place.