But that is obviously what players will tend to do, and if you don't understand that, then you probably shouldn't be a game designer (not you, personally, I mean generally speaking). Since the 5e designers were and are talented professionals, they knew what they were doing and what the result would be. They wanted half-orcs and mountain dwarves to be a bit better choices for fighter/barbarian/paladin types.
And I very much question the underlying logic that "because the species tends to be like this, therefore the player character's stats must reflect that tendency." That's my fundamental beef with that kind of paradigmatic thinking. It's basically an attempt to constrain player imaginations. It's absolutely fine to tell the players that a typical orc is like this or a typical elf is like that. But don't try to coerce them to be a typical orc or elf.
Edit: the whole history of D&D has been a slow movement away from trying to prescribe those sorts of decisions that should be left to individual players and DMs. That's a good thing.