As others have mentioned, stat allocation is a remnant from 1.0 where classes could make use of more than just one stat. Since that time, the stat system has gotten simpler and simpler to the point where stat allocation is now a no-brainer: drop everything into Main Stat and call it a day.

Remember when tanks used to get no damage boost from VIT? Or that DEX used to improve shield blocking rate? Pepperidge Farm remembers!