Each path requires a different weapon for some abilities. Str has an axe. One requires a hammer, one requires a piercer (agi i think), one requires a sword.
The purpose of this is too make the SK class more diverse so no one is the same. They are trying not to run into the same problem they did in EQ1. The issue being that each class had AAs they NEEDED to be effective. With the way they have it now each SK can pick which path he wants, and therefore making certain people more effective in some situations and less effective in others. Thus diversifying and still keeping each path useful.
For example, if you take the AGI path you need to be on a mount for a bunch of the abilities. Making this SK more effective at tanking mobs outdoors but less effetive in dungeons.