Upvote:2
In [the Middle Ages], surgery was seldom conducted by physicians, but instead by barbers, who, possessing razors and coordination indispensable to their trade, were called upon for numerous tasks ranging from cutting hair to amputating limbs.
I doubt it has anything to do with any scarcity of tools. If tools are rare, people with the skill to use them well are rarer still.
You get a barber to shave you or cut your hair because they can do it properly, without harming you. You don't want to let someone near you with a knife who would more likely than not cut off their own finger or accidentally nick your carotid.
Such people would have been useful for battlefield surgery as well.
Medieval barbers were trained through a system of apprenticeship, so during that time, they would have had their masters' tools to work with, and gotten their own when they "graduated" (or whatever term was used back then).