It's handy when flinging an arm over the back of the chair or holding a mug.
In my case, I put an apple magic mouse scrollball between Esc and F1 on a keyboard a decade ago, and still use this. (google `apple scroll ball keyboard` if interested)
(A recent oddity I noticed is that Firefox ignores up/down scroll if mouse isn't over the window, but side-to-side scroll still works.)
When I was using a surface that didn't even have 1 page up key on the bottom row, I was also remapping the unchorded shift keys, and created a chorded mapping for enter so essentially: - caps lock is Esc when alone, Control_L when chorded - enter is Enter when alone, Control_R when chorded - shift_l is Page Up when alone, Shift_L when chorded - shift_r is Page Down when alone, Shift_L when chorded
It was very efficient: doing Control L with one hand was much easier from the right hand side
Shift-Space also works as PageUp.
But TBH I've previously remapped the shift keys as extra page up, since when pressed and released they do nothing which is a waste for such a big key that's so easy to reach!