Weight, an intrinsic and inexorable property of all matter. The direction for that push force is down when the weight is greater than that of the displaced media, and up when it is lesser.
It's really the normal/standard take, and has been for around 2000 years.
Because that is what (effective) weight is. It is a force directed downwards when the weight of the object is greater than the media it displaces.
There are more speculative reasons for why density separation occurs, but sometimes laws are just laws - scientific bedrock.
Always! It is the most honest answer to most questions.
There are many answers for "why down", but i can understand why they don't seem satisfying to you in lieu of your educated imaginary "pulling force".
You’re describing weight as a pulling force, are you not?
Of course not. (effective) Weight is a pushing force (when it is heavier than the media it displaces).
That’s an interesting take. Where is the push force coming from?
Weight, an intrinsic and inexorable property of all matter. The direction for that push force is down when the weight is greater than that of the displaced media, and up when it is lesser.
It's really the normal/standard take, and has been for around 2000 years.