When a British Queen Marries, why isn’t the Husband called the King

Why isn’t the British Prince (Husband of Queen Elizabeth) called the King?..

Because the Queen is in the British Royal line, not the Greek Prince. And a King would be higher in rank than a Queen.

The rules are:

• The husband of a queen is known as a Prince consort and does not become King.
• The wife of a king is a Queen consort and does take the title Queen, although she does not rule as the monarch.

Those rules maintain that the one in the British Royal line remains higher in rank than the one outside the family that marries in.