A similar question has been asked on LinkedIn.
I don't think your assumption "handle is always pointing right" is quite true. ;-)
An icon is simply a representation of an action, and there's no "universal standard" regarding the visual appearance they should have...
Bing search icon:
Google search icon:
Search result for "magnifying glass icon":
I think it's mainly practical- when working with the smallest icons (say 16 x 16) it would take up too much space/too many pixels to orient the glass vertically, so by tilting it you can show more detail (bigger lens and bigger handle).
As to the bias towards right handed, I do think that reflects the bias in the population.
As bigger players use symbols to mean certain things then it starts to become a standard.
Find/search is not yet a standard from what I can tell.
In the Microsoft standard to the right is magnify and to the left is search.
Guidelines for Segoe UI Symbol icons