1. TRACTION. Meets often start early in the morning when the ground is still wet. Spikes literally spike the ground and add much-needed traction.
2. PROTECTION. Since cross country courses usually traverse open fields with uneven ground, wearing a snug-fitting shoe like a spike makes it easier to react to changing surfaces, which may prevent an ankle roll, or worse, a sprain.
3. SPEED. Lightweight shoes reduce overall exertion (less weight to carry). Plus, traction combined with less weight might be the difference between an OK day and a PR (personal record).
Bonus: Since most of the time they’re only worn during races, spikes last longer than training shoes.