Why Wasn't Princess Leia Organa a General in the Original Star Wars Trilogy?

This is a question I think about quite often because I wonder why it took decades for her to finally acquire that title years after the Rebels fought against the Galactic Empire? In the Disney trilogy, Leia is one of the Generals in charge leading the Resistance in the fight against the First Order. I know there's a Disney Star Wars novel that explains how she became a General but despite being a big Star Wars fans I haven't read a lot of the books which I'm trying to fix that.

Whenever I watch the original Star Wars trilogy, I always wondered why Luke Skywalker and Han Solo were promoted to Commander and General respectively. Meanwhile Princess Leia didn't receive any advancement. I know in A New Hope, Darth Vader mentioned her title as a Senator but while she was being held captive by the Empire, Emperor Palpatine dissolved the Senate. Which made her title as Senator absolutely useless leaving her only with the title of Princess of Alderaan. However, as Princess of a planet that no longer existed, in a way, that title was also rendered useless.

What I love about Princess Leia is that she's smart, strategic, brave, kind, stubborn, bossy and relentless. These are qualities that make her such an interesting character and not to mention her strong sense of duty to do everything she could to help the Rebel Alliance succeed in their fight against the Empire. I always found it disappointing that she didn't get a promotion. I know the Alliance was not a formal military organization but Leia was a leader however without a title. She didn't need a title to work hard to save the galaxy but it just would have been nice if she had received one instead of years later due to the creation of the First Order.