There are actually still some cases where the hemispheres will be separated, but they’re only in really sever cases now.  Apparently, there’s something called Rasmussen’s encephalitis, which is a disorder characterized by a lot of really bad seizures, so a hemispherectomy is one course of treating those patients.

I can think of at least a couple of super heroes that decided to become one, but even they had their catalyst… Batman… Iron Man…

The man who had a bunch of his hippocampus removed is named Henry G. Molaison. The surgery was back in 1953.