Why do so many semis equip their front tyres with spikes?

Spikes or metal spikes are commonly installed on the outer edges of the front tyres of semi-trucks.

It's common to refer to these as tyre chains or snow flaps,

and their purpose is to help vehicles gain traction and control in hazardous conditions.

They also aid the truck driver in maintaining control of the vehicle in slippery or slick circumstances,

such as during turning.

They help with stopping distances and cornering ability,

especially in wet or slick conditions.