The thing is many of these people could have a reasonably high quality of life in the conjoined state. Certainly it beats having moderate to severe intellectual disability. It seems that good neurological outcomes for both twins are only obtained in what’s termed partial craniopagus, with less extensive shared venous drainage. Nevertheless surgeons persist in attempting separation, sometimes even telling parents the possibility exists of producing two normal children. In the first case Ben Carson was involved in, for example, both siblings had to be institutionalized, and the mother regretted the procedure immensely.