Why are stat standards different for each type of weapon?

[isCasted]

Everyone here knows about how damage formula works in PSO, PSU and PSO2 - it's all same (ATK-DEF)*common_multipliers.

In PSO and PSU each weapon kind had different stat standard in order to balance out different aspects of weapon (Sabers had highest ATP because they were single-target, Swords had slightly lower ATP because they hit multiple targets, Daggers had even less ATP but they hit twice), because that common_multipliers part was same for all weapons. This had its side effects, like weapons with less ATP becoming OP against low-level/Zalured enemies and/or if user is under Shifta, but it could make sense.

In PSO2 this mechanic pretty much vanishes, here are some facts to it:
1) each weapon gets own multipliers for basic attacks. TMGs can have around same ATK as Partizans, but their DPH is significantly lower;
2) primary damage source is PAs;
3) enemy defense is so low (something like 300 S-DEF for lv65 Rockbear? Compare it to 2000-2500 ATK that players can have at that point) that the actual ATK value doesn't matter by itself;
4) buffs suck. If you use different kinds of weapons, your playstyle won't change even when you stack all the possible buffs (affixes, drink, Shifta/ride, tree buff, whatever ones left).

So... Why are stat standards different for each type of weapon? Why can't weapons of actually equal power have same ATK if everything is handled by attack multipliers anyway? If it doesn't matter that much, why does it have to add extra "deep" to the game? Why should it force you to switch to a weapon with higher ATK when you release PB (if you care about any but Ketos, that is)? And most important: why should it confuse new players?

[Stickboy]

because sega