The odd thing is that such a simple act as turning on a light is regarded as work. Or is it not allowed for another reason?

I may be off base here, but back in the day I remember learning (or hearing) that turning on a light is an act of creation (i.e. closing the circuit to create light). So, the act of not turning on the light honors the fact that no creation/work took place on the 7th day.

Perhaps someone else might be able to clarify.