It`s not because a console sees some increase in HW sales that we should expect a correspondant growth in SW sales in games.
What i mean is, it`s not garanteed that all those who bought the last game will be buying it again + a percentage of those who bought a Vita since the last game came out.
The HW increase hasn`t been great enough to assure that, no matter what, the game can grow in sales this year aswell.

Look at Wii U: games like Splinter Cell aren`t being given the full port treatment because Ubisoft knows the install base isn`t there to maximize profits. And i could use other examples.
As Vita, Wii U hasn`t grown enough to ensure developers that they can spend more money on ports.

Problem of the Wii u is people will always prefer multiplatform on Sony and Microsoft consoles.

About Vita nobody know the future so a real port of Fifa could do bad but it could do quite good, and i hear it's easy to port a ps3 game on Vita so i don't they would cost them a lot of money to make a great port,if they don't want to do some risk,Ea should not even make a Fifa on Vita because  it will bomb ,the first fifa sold 0.48 second does 0.22 this year it would sold less then that

At the start of Wii U`s lifetime that really was a problem. Also, it didn`t help that Fifa and other games were already in the market before it came out. But when the userbase grows, so will that potential userbase grow aswell.

No one knows the future, but they know the sales of the HW. And in their mind they see a userbase for that game and, to them, it doesn`t pay off putting the extra effort (money) to add extras to the game.
If the 3DS or Vita sales for Fifa suck this year, you can bet that next year, chances are a new version may not even arrive.

Every year fifa on psv/3ds/wii u are always the same so even if we don't get a fifa in 2015 it's not a problem because i can buy the first one.

For me EA lose a chance to generate more profit with a good fifa on Vita,many games sold well on Vita despite the low user base Call of duty,Uncharted and Assasin Creed.

Except Wii U isn`t even going to get it this year. PES included!

And it`s not like Fifa didn`t sell well. Last year`s version is missing the US sales. i saw it declined in Europe - probably dropped in the US aswell - but that`s not the most important thing.
It`s not that i`m saying that EA made a good decision, it`s that i understand why they did what they did. If, in their eyes, the attach ratio would be the same, why waste more money on making a better Vita game, when all pointed to not making more profits in the end?
But the games you mentioned were high profile and exclusives, so it`s natural for the attach ratio to be higher than a port.

So the serie is in decline on Vita that mean they got less profits with Fifa 2013 at least if they make a good port there is only a possibility they  get less profits,if they think people will buy the same game every year they are wrong.