The suction valve bends inward as the gas flows into the compressor and bounces back when the piston is at its right-most position. Similarly, the release valve bends outward as the compressed gas is released and bounces back when the piston is at its left-most position.
High-efficiency compressors operate at high frequencies and thereby develop heat. The valve steel must have the right properties to handle high temperatures over time.
For the compressor to work, the valve steel must be strong enough to handle both repeated bending motions and impact.
The thinner the valve steel, the less force is required to bend it. Meanwhile, a thinner valve steel leads to less flow loss at the compressor inlet and exhaust.