The original wording explicitly mentions "discovery or invention within the field of physics", so that wording has been reflected in some of the prices over the

The original wording explicitly mentions "discovery or invention within the field of physics", so that wording has been reflected in some of the prices over the years. Also, it's a price based on a will from over 100 years ago, managed by a private institution. The institution can be as arbitrary as it wants. They don't need to answer to anyone.