In order:
- Because race essentialism is a false and pernicious ideology IRL that has done much harm to a lot of people, and things which perpetuate it should be altered so they do not do so. Also, because real variability in actual living creatures is more than sufficient to make beings who fit anywhere on the "this is something a mortal being can be" spectrum, thus it is not merely laudable, but truly more realistic to embrace that variability in playable characters.* Playable characters, I would note, that are already going to be weird for their race no matter what, because most people don't have class levels.
- I already support using this, so I have no criticism for it.
- Same as the first answer to #1, but also because culture is an idea, an ideal, a trained or learned thing, not something baked into a person's genetics. You can take two identical twins and raise them in different cultures and, guess what, their cultures will be different! Physiology can have an influence on culture (e.g., as I've said in previous threads, dragonborn mature faster, lay eggs, and have breath weapons; this will affect them regardless of the culture they grow up in, and a majority-dragonborn culture will be affected by this.) But physiology does not, cannot, should not dictate culture.
- Setting-specific divinities are individuals with their own preferences; if they choose to favor a specific race over other races, that's their prerogative. It has little to nothing to do with the physiology of any given race, and everything to do with that deity's preferences. You may have noticed, for example, that the Romans enforced syncretism of their deities upon every culture they encountered. Worship is a cultural thing, and thus taught; divine favor is an individual-deity-personality thing and thus completely separate from the question of physiology.
Or, in sum? Because there are both unpleasant implications of #1 and #3 when these things are treated as
essentialism rather than as real and IRL measurable variability (for #1) or as the product of training/learning aka "acculturation" (for #3), and because it is
more grounded, more like the way real things actually behave, to
not make these things into examples of race-essentialism. Those unpleasant implications
can be avoided, thus, barring some other even more pressing concern, they
should be.
*See, for example, the results of
Anthropometry of Flying Personnel - 1950, G.S. Daniels. TL;DR: There is no such thing as an actually average person. Just two or three requirements (if strict) or five or six (if somewhat looser) is enough to exclude the vast majority of the population, and "exactly +2 Str, +2 Con" or whatever is certainly going to be quite strict. Or, for another example, the Australian Bureau of Statistics openly stating that, in both the 2011 and 2016 censuses,
the average Australian does not exist, because no individual person has all of the average (or, for non-averageable things, most common) characteristics, despite this being based on the full population data of their nation (over 23 million people.)