There's not enough ability to research it. You're taking big risks that require getting permission from a separate family, with only a guess that it might do something useful.

There's not even much in the way of data as to why it worked in this case, or others. But afaik, it's only ever been tried in multiple births, and only ones that are in distress. That's why this was even tried; an effort to save a struggling preemie.

Not that research is impossible, but the barrier is a big one.