Why so little in body image stabilization?

OIS was the first, as it was developed during film days. Not possible to shift a strip of film.

Minolta developed the first IBIS, largely to get around C/N's patents on OIS. The first efforts weren't quite as good as the best OIS, but the gap has been closed and even surpassed in recent years.

And IBIS was too jittery for video, until the electromagnetic IBIS that Olympus recently developed came along. It not only works with video, it adds one thing that OIS can't do: roll stabilization, eliminates the jell-o effect. As that system is used on the EM5 which has an EVF, the VF is also stabilized. I will say, having used it for about seven months, the EM5 IBIS is noticably more effective than any IS system, OIS or IBIS, that I've used in the past.

So, as of today... C/N probably stick with OIS because they already have a lot of OIS lenses, and as the two systems are fairly close in capability, it wouldn't make sense for them to spend a fair amount of R&D funds, possibly pay patent royalties, for what would be at best a modest gain in capability. And that assumes they could develop an IBIS system as good as the Oly EM5 has, which is quite a bit better than previous IBIS efforts from anyone.

Curiously enough, Sony used IBIS on it's Alpha DSLR's, but OIS on it's NEX cameras. Go figure...

Panasonic uses OIS on a lot of its M43 lenses, likely from their video roots, so with M43, one has the opportunity to choose which system they want to use, if they have an Olympus M43 body and Panasonic M43 lens.