My theory is
People buy it because it “beginner friendly” like it always IPhone 7,8,9,12 or 12s,13s etc than Android confusing line up of names and products like the Fold samasung
And the interface also good for beginner “to the point its childly easy to navigate and feel”
Every iphone last longer and still relevant for years after released, people who use iphone 7 still doing okay. Meanwhile Samsung Galaxy S7 already obsolete and slow.
Beside that reason, i think both of them are getting more similar.