That part I get. What I don't understand is why it needs to be prescribed by wotc in the player's handbook. A game with floating asi as the default rule is perfectly capable of producing the play experience and archetypes you mention.The argument has been made many times. Elves as a race are more dexterous than humans, so that should be prescribed in the racial bonuses. Dwarves are more hardy(+2 con) so that should be prescribed in the racial bonuses. You can argue that you don't agree, but you can't argue that the arguments have not been made.
The way I see it, there are a few dials that dms and players can turn in 5e to make it the kind of fantasy they want. Floating racial asi just adds one more little dial. You turn it one way to get dexterous elves and reinforce that archetype, I turn it another way to reinforce archetype of class (e.g. a dwarven rogue who is as agile as any other starting rogue). You turn it one way to get what represents to you a species average, I turn it another way to represent the exceptional nature of the pcs.
All that being said, is it really about the play experience, since floating asi can accommodate your preferred play experience? Or is it more about the reading experience, opening them up and finding the familiar tropes present and certified by the game's creators?