1. To represent a timeless and classic look. A wedding band is a representation of a couple's commitment to each other and is seen as something timeless and classic. A simpler, more elegant design can help achieve this.
2. To make it more comfortable to wear. Sleek, plain rings are usually more comfortable to wear, since they are not overly bulky or heavy. This means wearing them won't cause discomfort or impede any activities.
3. To ensure it is durable. Simple bands are more durable, since they contain fewer details and decorative designs. This makes them less likely to chip or break, and they are more likely to last through everyday activities and various occasions.