You are looking at a skill as being only one skill though, like gold. Useful skills are rarely like this, they are groups of skills, like groups of muscles. To overwork one doesn't make up for the underwork of others. It isn't about having a massive diversity of fields, it is about all of the skills layered within one specialty. You may want to only practice with the sword but, there is a skill involved just to draw it from the scabbard.