It's important to remember in almost all European Monarchies there is only a single monarch. There are tons of titles for families, children - both illegitimate and legitimate - and mistresses as well as court loyals alongside traditional hereditary titles of nobility under the suzerainty of that monarch (dukes, earls, counts, etc.). We tend to think of queens as being one step away from the monarch in terms of rank (and many, many queens were able to exercise a great deal of soft power and influence with their position), but that is generally inaccurate. The next in rank to the King is his younger brother, then any male cousins or uncles until he produces a suitable heir to take the throne upon his death. With most Monarchies possessing salic laws, only males could hold the position of monarch, or be designated as heir. England, and later the United Kingdom, didn't have a salic law, so females can be the monarch or heir based on primogeniture.

So, outside England "Queen" wasn't an actual rank in the same way as a king, prince of the blood, crown prince, or other hereditary noble titles passed along male bloodlines, but rather a designation of the monarch's wife with whom his male offspring would be considered legitimate and able to inherit (and, theoretically, could be bestowed on anyone - even a commoner) in a monarchy possessing salic law. However in a non salic law monarchy the Queen is the monarch, and her husband is now in a similar situation to say a Queen in France - their offspring are legitimate, he has access to the royal person and weilds a great deal of influence and soft power, but is not a Co-Monarch which somehow shares the crown as we might sometimes imagine (I think Ferdinand and Isabella of Castille and Aragon are to blame for this misconception as they were Co-Monarchs of two separate kingdoms that would go on to combine to make Spain, but this was an incredibly rare association in Europe).

Since the UK's monarchy is so unique it flips the titles a bit, and a more accurate way to describe Elizabeth Windsor, her predecessors and successors, would be the non gendered "Monarch" or "Sovereign" , rather than King or Queen, but tradition dating back to Elizabeth Tudor would have her titled as Queen upon inheriting the throne. Either way, her husband Philip Battenburg is the Prince Consort only, since naming him King would define him as the monarch when he is not (the Battenburgs have held many royal positions, and members have been kings and queens of various nations, but not the United Kingdom, while Elizabeth's father was King George VI, from whom she inherited the throne) and technically would've made Queen Elizabeth II the Dowager Queen (meaning whoever would marry her inherited the kingdom as her dowry, which would have been accurate for Elizabeth I and is why she never married). The next King of the United Kingdom will be King Charles III (assuming he uses his name as his regal title when crowned) as he is the eldest child of Elizabeth II and Philip Battenburg.

To sum up: there's only one monarch, and calling someone a king when it isn't them is confusing, so they came up with a more confusing system of titles instead.