There are 2 reasons to remove your winter tires in the spring.

Winter tires are built for winter weather. They are built with a much higher percentage of rubber
which keeps them supple (softer) in low to sub-zero temperatures. The softer material
provides more traction on cold wet surfaces.
Operating winter tires when the road temperatures are higher cause the softer rubber to
degenerate more quickly; as stated they are not designed for hot road conditions. Exposing winter
tires to very hot road conditions increase the risk of a blowout which can cause the driver to lose
control of the vehicle.
Winter tires decrease stopping distance in the winter because of softer rubber and high tread blocks
but the opposite happens in the summer. Using winter tires in the summer increases braking
distance by up to 10% on dry pavement and up to 26% on wet pavement
Results are clear, save money and increase safety by changing your winter tires to all season tires
each spring.