Because it looks like the eye of a tiger
Glowing lines of yellow, red or blue, which move when you tilt the stone.
Originally this stone was called Cat's Eye Quartz (18th century). The effect is due to asbestos which has metamorphised to silicate.
The blue form is called Hawk's Eye. Blue asbestos becomes golden brown when oxidised.
Usually you only see polished stones of Tiger's Eye. The specimen at the top of the photograph is natural unpolished Tiger's Eye, and it still gleams.
Larger pictures of Tiger's Eye:
These specimens are polished (tumbled). These two photos of the same specimens show how the stripes of colour vary.
This is natural. The shiny stripes are less obvious, but can still be seen.