glassdon't you have this backwards? i thought one of the reasons they implemented it was so that pub medics would start healing scouts, since they never did before.
i assume they still don't, but from valve's perspective it was worth a try because valve only cares about pubs.
At the time at lot of the changes were to make medic more enjoyable to play in order to entice people to play it in MM. Because MM doesn't have have any mandatory classes, and people can choose any class, it makes sense to make medic as enjoyable as possible so there are more people who are willing and actually like playing the class in MM, instead of just ending up with a no medic team, or bullying a player into going medic. The crossbow buff and medic movement were apart of that iirc.