3 die 6 rolls for a nice distribution of possible rolls with the most common being 10 or 11. Making the average 10.5.
With 4d6 drop lowest you wind up with 13 being the most common result.
Going further into average roll results with 4d6 drop lowest for six attributes you typically wind up with:
16, 14, 13, 12, 10, and a 9.
Once you know those numbers you can then design a system that mimics those results via a point buy system. Usually point buy systems allow for that exact distribution or something very close to it. Then the game system balance is designed around those results.
From there the evolution of point-buy systems (which remove the randomness that many people dislike) wound up having, typically, 28 points to use or 25 points if it was a 'pathfinder' (in pathfinder the price of an attribute increase goes up as the attribute goes up so to go from 10 to 11 is one point to go from 11 to 12 is 2 points meaning that to raise from 10 to 12 is a total of 3 points) system which limited how low you could drop a stat in favour of extra stats.
And... from all of this we wind up with the attribute generation systems that we find in many games.
I get that this is D&D legacy. My point is that it was good simplification of system for people who don't have CPU for a brain that would need to calculate several things at same time in each part of turn, making it chore to play. But this is computer game, you don't need simplify math for people because CPU does all that complex stuff for you. I mean you can if you want take those points upon which for example attack is made and calculate it yourself but there is no point to it as CPU presents answer for that instantaneously. So you could increase complexity of system, creating more depth to it at same time making it easy to understand at basic level as player don't need to actually do the math but know what happens in good/bad result of changing those stats.
I don't think rolling dices for main stats for creating characters is best part of D&D. I mean sure it is part of roleplaying if we create character which is unknown to us and which will be only ruled by law of probability. Which means roll dice for character creation is only really needed when you don't want to create yourself character and leave it to statistics hoping you won't end up with completely bland character with 13 int trying to be a mage.
Sure there is something enticing about it from RP perspective and i do love to play like that from time to time but system itself could be easily reproduced (statistical probability of it) without using actual dices like for example creating system on inverted part of parabole which is moved to only +x,+y where x is for example stat from 1 to 10 and y is chance to get that stat. So like in roll dice case you would get mostly 4-6 where 1 or 10 would be very rare. With it you have clean system without weird fluctuations like 1-18 because that is best for dices not for actual gameplay.
I get that PoE is back to good old days of BG Torment and so on. But they can't use D&D and frankly people remember those games from D&D2,5e not 3,5 which by all acounts only ToEE get right (with problems). So they are creating game based on successful RPG from using completely different mechanics at core to their system which they base on later D&D which no game beside ToEE (which was turn based !!) got right.
And they have partially did what i wrote above with for example turns-rounds system compared to D&D.
Mind you this is not critique of system in PoE. I can't criticize it as i haven't played it yet. It\s more of opinion piece of how PnP RPG and cRPG world are different and how each of those worlds have both ups and downs. Namely PnP RPG world needs to simplify systems behind it because players can't spend 99% of their time doing math where due to our brains and lack of linearity GMs can create any scenario they wish, where cRPG can create deep gameplay system with complex math showing results to player instantaneously at a cost of flexibility and completely predetermined path/paths made by devs.
So my point of this piece is that with cRPG system designers should use those ups that power of CPU gives them. If you for example shoot in PnP you need to have very simplistic math because anything more than few stats to take into account would create complex string of actions that needs to be calculated where for example shooting in cRPG could take as many variables as it wants like wind speed, curvature of planet, mass of bullet, friction of air, temperature of air, rotation of bullet, and so on to deliver deep ballistic system which later can be translated into simple form of % to hit instantly and suddenly rising intelligence for sniper is valid as dude who has high int could better shoot at long distances, perception then can be used to determine if sniper can even see object at a distance. Or mage that draws power of magic via his stamina where for example his endurance is important to pool of stamina, strength is important to somatic elements of spells over long time, charisma to linguistic elements of spells, dexterity to complexity of somatic elements and thus very important for high level complex spells and so on and so forth.
So creating system in which all stats matter because you have instant result for every math calculation creates situation in which amount of specialization of classes rises exponentially without even need of abilities that changes rules that governs player character. Suddenly you can create mage that specializes in long battles a War Mage which has big reservoir of stamina for spells and high strength to cast somatic spells over long period of time hours or even days of battle. Or you can create mage that specializes in non somatic spells charisma driven at cost of type of spells he can use he can empower those above what is available to all rounder. Then you can add abilities, perks, traits, equipment and stuff and suddenly you have shit ton of various build you can explore for weeks, months or years which would never be available for PnP game due to finite amount of human patience to solving math problems when you are playing PnP.
Sorry for this Think-Thank dump.
edit:
It is also not only about main stats but about every system math problem involved like calculating armor, hp, actions, spell power and so on.
