On the issue of racial stat boosts: There is an obvious functional use for the stats, as a way to bump up your purchased stats (using that as a baseline) to a level that provides the overall balance desired for character creation. That is, you get your 27 points, plus another 3 points in stats (usually). Thus it doesn't seem unreasonable to unlock stats from races, and just give a free +2/+1 at the end of stat selection.
However there are two problems with that:
- There are a few races where the non-stat bonuses are such that +2/+1 isn't appropriate. This includes both types of humans (+1 to two stats, and +1 to all), mountain dwarves (+2 to two stats), and tritons (+1 to three stats).
- While not immediately obvious, it seems that there is no race (that I can find) that increases both Str and Dex. You can use the human race to get +1 to each, but there's no race that will give you +2 to one of them and also +1 to the other. This appears to be a deliberate balance choice to avoid an obvious best choice race for combat.
Those two points make it difficult to make a rule to allow players to pick any two stats they want to boost, because there will be a strong preference to go for some combination of Str and Dex. Adding "exceptions" to rules (ie: "Choose +2 in one stat and +1 in another, but you cannot take a combination of Str and Dex") is generally looked down on, and it draws attention to something you wanted to avoid in the first place.
Even if you split the stats up in categories (eg: one physical, one mental), you end up with "Choose your primary combat stat plus Wisdom, because Wisdom is your most important mental saving throw" kind of advice. It also means you can't get Str+Con races, like half-orcs and goliaths. And as you continue to try to refine it, you run into more and more of these conundrums.
So by attaching the bonus to the race, they can prevent certain undesired combinations from appearing, while also giving a varied appeal to the races. Yes, you still get certain races being better for certain jobs, which helps encourage a bit more variety in race choice, as the secondary aspects of race choices (skills, spells, etc) have a much weaker effect on choice.
From an abstract sense, I'd prefer the Ancestry / Culture / Background / Class splitup in construction, but I can see why it doesn't always match up with how people actually make choices in character creation. The current Race/Subrace option is basically a merged Ancestry/Culture construction in order to deliberately limit players' choices, which can, ultimately, be beneficial.
In addition, it can be difficult to separate out a lot of the subrace benefits into culture benefits. For example, Sunlight Sensitivity and Superior Darkvision for dark elves is more intrinsic than cultural... probably. I guess if you lived underground all your life, you might develop those traits. Hmm.
Having said all that, I could see a somewhat more esoteric way to achieve this end. It still singles out Str and Dex, but isn't quite as troublesome in terms of how it is constructed.
You have 4 points you can spent to further raise stats, by +1 per point. You may not add more than 2 points to any given stat. If you choose to raise Str or Dex, you must spend 1 extra point for the amount you gain (ie: spend 2 points to get +1, or spend 3 points to get +2).
In addition to the above, you may spend one of your stat points to instead buy an extra skill proficiency.
This would allow getting either Str or Dex, but not both (since it would cost 5 points to get +2/+1 in the both of them). Also, if you choose to only get stats other than those two, you can also get a skill proficiency (since it would cost just 3 points to get +2/+1 in non-Str/Dex stats), which may be desirable to some people.
That would increase character design flexibility without being too much more of a hassle. Maybe.
