Stereotypic behaviors in horses - crib-biting, weaving, box-walking - are preventable with appropriate management from an early age, and are signs of chronic frustration rather than learned habits.
Stereotypies are welfare indicators, not vices. A horse that cribs or weaves is communicating that its behavioral needs for forage, movement, and social contact are unmet. Suppressing the behavior with physical devices while leaving the cause unaddressed is not a welfare solution - it removes the coping mechanism without resolving the distress. Prevention through appropriate management from foalhood is far more effective than attempting to eliminate established stereotypies.