I'd guess just because cw is much easier/faster to type (because c and e are pressed with the same finger) on a QWERTY keyboard.
Looking around, I can't even FIND a "c on first finger" fingering.
- https://en.wikipedia.org/wiki/Touch_typing#/media/File:Finge...
- http://www.typingme.com/touch-typing/typing-lesson-9.php
- https://agilefingers.com/articles/touch-typing-finger-placem...
- https://www.computerhope.com/issues/ch001346.htm
- https://www.ratatype.com/learn/
and on and on.