At the same time ALL throwing weapons takes a single slot so you are allowed to carry four stacks of them: you can carry with you 16 throwing spears, 12 jarids, 12 throwing axes, 32 shurikens (just to point out few examples). This is not realistic or historical at all, and can be a pain for the rest of the players (a xbowman carries 24 spending 4 slots too). It have great impact on the game. The balance may require that many throwing uses 2-slots so people don't abuse them.
Archery - Most bows 1 slots (rus and long are 2), all arrow types are 1 slot and the introduction of 0 slot 1h weapons to allow ranged to carry a melee weapon.
So, taking the long bow with bodkins as an example.. You get bow, 2 sets of bodkins (30, more when loomed) and a 1h weapon
Or you could go pure archery with the horn bow and have.. bow and 3 sets of bodkins (45, more when loomed)
X-bow - Most are 2 slots, bolts are 1 slot and once again the introduction of 0 slot 1h weapons to allow ranged to carry a melee weapon.
So, any x-bow, 2 sets of bolts (24 for steel bolts) and a 1h melee weapon.
Less bolts than archery but the reload time mean you get through less. This is balanced out by the additional power the X-bow holds over the equivalent bow, you can hold your shots for a long period of time, and have the bolt ready to release (once the bolt is drawn into the X-bow it remains there till shot). Finally and Maybe most importantly x-bow only requires wpf
Throwing - Majority 1 slot, a few low end are 0 slots.
Throwing daggers are low damage but you can have up to 32 (only 2 more than an archer with a melee weapon)
Thowing spears/throwing axes are heavy damage but can only carry 16 (much less than an heavy x-bow/arbalest with steel bolts)
Once throwing gets mixed with melee it becomes more complicated.. This is because throwing requires power throw and WPF (and unlike archery it results is a massive loss in ammo, no matter which weapon you use, throwing and melee weapon that is).
This means most people go mainly for melee and put a couple points on throwing just to throw on their way into melee. Personally I've found this to be a waste of time and prefer to have to characters (1 melee and 1 pure throwing).
I think especially with the recent buff to archery (archers don't complain have you seen how many more there are now?? I've even started using my archery alt again) and the not so recent nerf to heavy throwing axes.. The devs have done a great job in making these 3 classes as usable as possible without 1 being clearly superior to the others, or 1 inferior.
Finally, for your realism argument I'm not even going to bother having a debate as chadz has clearly stated the dev team are more interested in making a fun playable game than a realistic simulator .
(I have a throwing alt, archer alt and an x-bow alt)