They were skilled craftsmen,which soldiers were usually not. Soldiers had often no trade especially if they joined the army as young lads. As the article says the army usually hired skilled craftsmen but then began to employ them as soldiers on the army payroll.Later they trained them too so Signal Corps , Royal Engineers etc.
The army training was usually very good and a man could use the skills learnt in the army and earn a living in civilian life when he left the army instead of being in straightened circumstances as all too often was the case prior to soldiers learning trades. Viktoria.