Why can you, in the folder tree, open/close the folders with the right/left arrow key and in the pane you have to use Alt Arrow down/up.
Why can't you use the left/right arrow in the panes?
I'm a keystroke user so it's very confusing for me.
You can change the arrow keys to work like this. Just keep it in mind when using view modes other than details and power 
Because the arrow keys already do something else in the file display, and changing that would be very bad (especially in thumbnails, tiles, list, and icon modes).