Originally Posted by
Ryllharu
It's because it doesn't work that way. Usato had to figure it out instinctually, and as the other healer and his sister described, what you're doing is different every time and for every healer and every patient.
Curing himself of cholera was different from curing himself from being poisoned, which was also different from how he continually heals himself from exertion. He had to be uniquely attuned to what was going sore in his body where.
It's not something that works universally. This isn't "Cast Curaga" and you're back to full health without putting some actual thought into it. Even healing a broken bone took some thought on how to approach it.
That's why the rescue squad's priority is to Get In, assess who can be saved by the backline healers and who can't, Get Out as fast as possible, and don't let yourself get killed.