The Class A Uniform is not always worn in its full state. For certain events like the Birthday, the First Aid Meet (before it became a Class B event), and the Family Dinner scouts wear Class A; No Hats, which is exactly what it sounds like. There are also events like the Birthday, that require Class A Dress, which adds medals to the uniform. In addition, some events not only do not include the campaign hat but actually replace it with sailor hats.
Certain events may also require scouts to wear their OA Sashes if they are a member of the Order of the Arrow.