Thanks to Harbinger921 for the inspiration!

When creating Final Fantasy, Sakaguchi faced a problem: how will his development team represent battles?

Back then, Sakaguchi had to program Final Fantasy to operate like a tabletop game. In Dungeons & Dragons, for example, “Every round, each person acts once, from highest initiative to lowest. Your initiative is determined by rolling 1d20 + your Dex bonus, and stays the same until the end of the combat.”

For limitations in gaming software, real-time battles weren’t possible.

This is the basis of the turn-based battle system. Here’s a further analysis from a user on Gamefaqs:

The original Final Fantasy game was heavily based on the tabletop RPG Dungeons and Dragons. This is seen in various things, from the way spells were ordered into individual level charges to enemies like the behemoth (which originally used a sprite based on the D&D one which was renamed to EYE and had the image changed so as not to breach copyright in the North American version of the game).

One of the ideas taken from D&D was the concept of critical successes. Basically, dice rolls would determine whether or not you hit, and rolling a certain number would be counted as a critical success. The same concept was applied to the battle mechanics: any time an attack is made or a spell is a cast (with exception to the 300HP special specials) a roll was made from 0 to 200. Depending on factors like hit% vs evasion (or spell effectivity vs your hidden magic defense stat) a low enough roll would score a hit, and whether or not it was a critical was also determined the same way.

I used to think “how do I control four people at the same time in Final Fantasy”? Now I know…

The series slowly broke away from this method, because it’s an imperfect representation of the real-time battle structure. Why else did they decide to implement ATB, which would maintain the “flow of time”? This gives the player a sense or urgency in battle. Also, the developers tried to represent real-time battle the best they could, while controlling many different party members.

After Sakaguchi left, the developers faced a new problem: how do they represent real-time battle? Final Fantasy XII’s approach to this was automating battle of the other playable characters. Final Fantasy XIII and XV followed suit. Final Fantasy XI and XIV bypassed this process.

Everyone who’s ever wanted the series to stay turn based is forgetting two things about Final Fantasy. First, the series is always evolving. Second, turn-based is a representation of real-time battle. It was the best they could do at the time. Since they can actually program real-time battles, subsequent titles will feature more of them.

This has been their philosophy all along.