Honestly a fair question since all helmets are designed for hits to the head.

They all protect for a specific type of hit to the head. Simplifying your example to a bicycle helmet vs. hockey helmet: A bike helmet is likely to be hit directly from the front, it is lightweight for ease of riding, and it will sacrifice itself to absorb as much impact as possible, making it single use only. Hockey helmets are designed for multiple hits, and protection from a projectile. H hockey puck might punch a hole through a bike helmet.