Why do pilots use non polarized sunglasses ?

fuckyeahphysica:

Polarized lenses are not recommended for use in the aviation
environment.

While useful for blocking reflected light from horizontal
surfaces such as water or snow,

polarization can reduce or eliminate the
visibility of instruments that incorporate anti-glare filters.

Polarized lenses may also interfere with visibility through an aircraft
windscreen by enhancing striations in laminated materials (known as photoelasticity)

     Photoelastic visualization of contact stresses on a marble in a C-clamp.

and mask the
sparkle of light that reflects off shiny surfaces such as another
aircraft’s wing or windscreen, which can reduce the time a pilot has to
react in a “see-and-avoid” traffic situation.

– FAA

*Source:  Polarized v/s non polarized cockpit images