Thief>Ninja/Dancer Class/Job

[Nahara]

Because daggers are weapons that rely upon precision rather than brute force for the damage they deal.

At the same time, STR is the melee physical damage stat and DEX is the ranged physical damage stat; it says so right there on the tool-tips when you hover over them. They have very clearly defined purposes and it seems way more efficient to just keep using STR as the melee physical damage stat, then to change DEX's purpose for a single class.

On top of that, you can't seriously expect someone to believe gear like the Ballad attire or the Shikaree attire are thematically-appropriate for a Rogue/Thief/Ninja.