Why do all Final Mix games have English voices? I was never able to figure that out. 

Iunno.

The English VAs are much better.

The Japanese enjoy English voice acting. 

 

They used Japanese voices in HD 1.5 ReMIX.

I've always heard it's because the Japanese prefer English VAs in regards to Disney character voices. Not really sure on their opinion of FF and OC voices, although I do know Nomura did personally request some, like Mark Hamill for Eraqus.

i think in an interview once Nomura said that he thought the english VAs fit with the characters more but he never specified which characters

It helps them learn English

They like the sweet pipes of James Woods as Hades

I think its obvious they use the English voices because they have the NA version in english with more content, it will be more different than the original japanese game and then they add some new features and Tada! a new Final Mix.

Every culture has its purists.  While in the west there are people who insist on watching subbed anime over dubbed, there are Japanese who insist on watching subbed Disney movies (and games) over dubbed.

I've read some where that it is because that Nomura want to show Japan the English voices.

Why do all Final Mix games have English voices? I was never able to figure that out. 

Same reason why Resident Evil has English VA rather than Japanese VA. Because it fits the characters a lot more and the Japanese are very fond of the English language and culture.

Because Nomura made it so.

They prefer the English VA's.

 

TBH THe Jap. VA's are decent IMHO, except for Pooh, who has THE WORSE VOICE EVER, IT MAKES HIM SOUND LIKE A NERDY ROBOT.