So, hypothetically, what if every player wanted to play a Str 18 women in this world where women are characteristically weaker than men? Which ones do you say no to, and how would you justify that decision if you ARE allowing some women to be as strong as men?
If I were running that, I'd probably come up with a common Amazonian backstory for their strength - perhaps something that runs in their family, or perhaps a magic spring they all drank from. PCs often have shared backstory in my games.
Okay, but that doesn't answer the question. If not all of the players want Amazonian blood or want to drink from the same magic spring, you're going to either accept all their characters or say no to some of them.
But I made my point, which was to get you to admit that exceptional situations require exceptional justifications within the setting. Bringing this back to the main issue, racial differences (and gender differences too, if that's pertinent to the setting) matter.
But here's the thing - even with required stat minimum/maximums, you could just as easily get unlikely combinations. Players could choose to play all halfling fighters and half-orc wizards - choosing highest Int possible and lowest Str possible for half-orcs, etc. The only way to get PCs to be representative of their races is for strict in-order rolling of attributes and random-roll race.
I think you failed to realize that those characters would STILL be within the prescribed parameters of the setting. I'm unsure of your point since having a party of all average half-orcs doesn't track with the example of having all exceptional, beefcake women (in a setting you admit has sexual dimorphism).
And there's no reason that PCs should necessarily be representative. I played a half-orc wizard in a recent convention game and it was great fun. He wasn't typical of half-orcs, but no one thought he was.
It's almost like you don't read a single thing I write... or choose to ignore it when you think you can score a point. I never said characters couldn't be the exception to the norm. What I DID say was that it should be a negotiation with the GM.
EDITED TO ADD: In general, I don't think the racial attribute adjustments have all that big a practical effect on games. If that elf had a 16 Dex instead of a 17 Dex, it is a slight adjustment - but for the most part, I think the game would go almost exactly the same. What I like about it is that it cuts down on the urge among many players to min-max - i.e. "I'm a half-orc fighter because I want that +2 Str."
Now I know you're clowning. I've seen plenty of builds throughout my time with 3e, and more recently with 5e, that place the highest score to stack with the racial bonus, and sometimes then give the character a Feat to push it higher (usually to hit that coveted score of 20). Racial ability adjustments ABSOLUTELY encourage min-maxing. Just because you've been lucky enough to play in groups that don't, doesn't mean it doesn't happen.