Legacy design and use patterns. The top of the screen used to make more sense than today. Mobile-first design really hasn't taken hold for many UX web designer

Legacy design and use patterns. The top of the screen used to make more sense than today. Mobile-first design really hasn't taken hold for many UX web designers (and/or the organizations haven't adapted). Relatively speaking, large phones where it's difficult to reach the top weren't popular until recently. Even mobile apps are just starting to put navigation towards the bottom.