Insensitive switches that are on don't look active
Widget factory in busy mode:
Checked checkboxes and selected radio buttons are easy to understand, even when insensitive. On the other hand, switches that are on but insensitive are ambiguous and could easily be confused for being off.
The main place I've experienced this issue is in Software repository settings dialog, where it is hard to tell the difference between active an inactive repos at a glance, due to the use of insensitivity: