Different species have morphological differences, I hope you won't deny that. A comparative analysis of those differences results into a relative attribute spread i.e. racial stats.
The Ability score system doesn't reflect those differences. The actual ability numbers themselves are completely arbitrary. A numerical stat bonus may convey some illusion of representing racial differences, but it just falls apart under scrutiny. The first and strongest point of that scrutiny is that whatever morphological differences there are, we don't know them, and I fail to see why some ability bonuses that have been around as tropes since early DnD editions should be treated as the only source of truth. Are high elves naturally smarter than their wood cousins or do they simply tend to live different livestyles? In the end it's just an abstract game mechanic. It isn't realistic, it was never meant to be realistic and I see no reason to defend it on such grounds.
Of course the ability score system reflects those differences. Maybe not entirely, but usually at least the dominant (+2) racial ASI represents an inherent physical or mental difference.
Orcs have more muscle and a hardier constitution -> +2 Str and +1 Con Halflings are naturally nimble and a certain subrace is hardier -> +2 Dex and +1 Con Gnomes are flat out more cunning ("Gnome Cunning") than other races -> +2 Int. Elves are "magical people of otherwordly grace" -> +2 Dex Dwarves are physically hardier and some have "keen senses & deep intuition". Keen senses, at the very least, seem like an inherent and not cultural property. Tieflings get a Cha and Int bonus because of their physical demonic heritage. "Keener than normal intellect, as befits those linked to Asmodeus himself."
I'll concede that some ASIs seem more cultural (e.g., High Elf Int bonus or even Mountain Dwarf Str bonus), but this is not often true for both (or sometimes either) ASIs of a race.
