I am just wondering why there are three different types of regular arrows available.

The ranger gets 3 ammo 2 weight arrows in their starting gear.
The thief gets 5 ammo 1 weight arrows in their starting gear.
You can buy arrows that are 3 ammo 1 weight.

Is there a reason that thieves start with far superior arrows then rangers?  Can you buy more "thief arrows", or once you exhaust your starting arrows you are stuck with regular ones?

Also the Rangers extra heavy arrows means it's almost impossible to start the game not overloaded.

It seems overly overcomplicated to have 2 class specific types of arrows, one of which is far superior.