Are UI developers all left handed?

[John Moser]

Put your mouse pointer in the middle of the screen.

Put your mouse somewhere you can grab it.

Now reach out and grab the mouse.

Where does the pointer end up?

If it winds up in the top right of your screen, it seems you're right
handed.  Your arm just goes that way, and your wrist straightens to
support the movement.  It flexes outward more easily than inward, too.

UNITY.  Puts the control box (close, minimize, etc) in the top left.
Of the entire screen.

GNOME SHELL.  The thing you have to hit to do anything is in the top
left corner.  Want to log out?  That's in the top right, fastest thing
you'll be able to hit ever.

EVERYTHING puts menus left to right (the Help menu used to be on the
far right, separate from all other menus, in Windows 3.1), but that's
probably more for left-to-right text flow than anything.  Also it
keeps "File" from being too damn close to the big evil [X] button, but
it's still slow and inconvenient.

Why do UI designers insist on designing interfaces for left handed people?