Presumably if a job really needs to be done, someone is already being paid to do it. So conscription would require that a whole new level of make-work be devised to give the conscripts something to do so they don't get into troubble. They don't know how to do anything, and by the time they start to learn a skill that has some value they are done with their service.

Russia has conscription for their military, and how is that working out for them on the battlefield? Not too good from all accounts. I understand that professional NCOs in the Russian forces spend most of their time hazing the conscripts and shaking them down for money. They are just cannon fodder anyway.