I don't know.

I have two theories: one is that the feline and canine eye is much more sensitive to a spot of monochromatic light, so it's really bright to them. A torch beam, emitting a wide spectrum of light, looks more like a sunny spot in a dappled shade, which their predator's eyes are more used to filtering out to find the hidden prey within.

The other is that the way it reflects, to an eye that isn't close to the beam, is distorted; so that the moving spot appears to be within the carpet or whatever. We don't see this because we're usually close to the emitter and thus see the reflection fairly close together. But that's an outside bet - I favour the former.

HTH,

Paul