In C#, a static class is a class that cannot be instantiated. Static classes are created using the static keyword in C# and .NET. A static class can contain static members only.
Since you cannot create an instance of a static type, the behavior of static struct would be exactly the same as the behavior of static class. So, there is no reason for creating them. I think it would be theoretically possible to have a static struct but it would be confusing - how would you choose between static class and static struct if the behavior of the two was exactly the same?